I hate to tell you this, but even with context that sounds pretty bad. You acknowledge that the rules are there to give the players an ability to assess risks and rewards, but then at the same time you say you throw out the rules and just wing it based on what's "cool," and that you may rather arbitrarily apply the rules or not apply them based on whether it's "cinematic and cool."
As a player, statements like this terrify me, because what you actually mean is that I, as a player, can't actually assess risks and rewards, and that rather than playing to the rules, I'm playing to the whims of the GM. Should I try to get the high ground? In a consistent system that grants a consistent high ground bonus, then yes, I should always be trying to get and maintain the high ground (which is exactly what you'd do in a real fight). But when playing against the whims of the DM, you can't ever really know if your tactics are sound, because one day gaining the high ground might amuse the DM, or it might bore him, and you aren't going to know until after you try.
There really is no way of discerning a "good idea" from a "coin flip" from a "bad idea" when the rules change based on the DM's whims or what he or she find personally entertaining and amusing.
Either I wasn't clear or you're projecting from bad past experiences. I explicitly want players to be able to figure out whether something is a good idea or bad idea. I also want them to play tactically. I just don't want to stop game play to look up some piece of minutiae that really doesn't matter, in the long run. You don't have to know whether standing on a table gives a +1 bonus, +2 bonus, or advantage to know that it will be beneficial. You can also ask what the bonus will be
before doing it.
If the rules say it's a +2 bonus and I call it as a +1 bonus, in play, there's definitely an argument to be made that it was a "bad call" because I cheated the player out of a 5% chance of hitting. I don't find that a particularly compelling argument,
for the style games I tend to run, for a couple reasons. First, that 5% difference is exceedingly rare in making the difference between success or failure in a scenario or life and death to a PC. Second, the long game tends to see me call it as a +2 when RAW says it's a +1 -- especially considering that I intentionally try to favor the players when I'm shooting from the hip.
The other side of the argument is that I'm cheating the players out of game time by pausing things to look up a rule rather than trust 35 years of experience running games and knowing the "spirit of the law". This is the side I tend to favor and to view as my "job" at the table. I'm the referee, to use the word Gygax used. No rule book can actually account for every situation. The referee's role is to ensure sanity prevails.
Going back to the example of higher ground, we both seem to agree that it has some tactical benefit. I'm pretty sure that 5E doesn't have a specific rule around it, though. So, what does a GM do? I could stick with RAW, but that (IMO) is unfair to the player who is thinking tactically and trying new things. So, I do not feel constrained by RAW. I will give them a bonus, if it seems appropriate (in this case, we're saying it is). Does the exact benefit depend somewhat on my mood? It would be silly to say otherwise. I'm human. Even trying to play straight-up RAW, I sometimes let my knowledge of tactics unconsciously bleed into dumb monsters' tactics. I try to be fair or slightly in the PCs' favor, though.
So, what happens if I make the call to give them a +2 bonus for higher ground and it proves effective enough that the SOP becomes everyone starts looking for higher ground? Well, that doesn't seem right, to me. Higher ground is nice, but it's not the end-all of combat. I probably got the +2 wrong and need to drop it to +1 (or, require an acrobatics check to climb onto a table during a melee, but let's keep it simple). That change didn't come out of pure randomness or spite. It came out of observing the impact of a call on the game and seeing undesirable effects. What would actually happen is that I'd notice the impact during a given combat or on reviewing the session, afterwards. I'd then let the players know
before they tried it again that I wasn't comfortable with the way things were going and wanted to revise it. They might talk me out of it, but they might not -- as GM, the final call is mine, though.
It's also possible that I make the call as +2 and no one uses the tactic for another six months -- long enough for me to forget a specific one-off ruling -- and I call it as +1 the next time. My gut reaction is that the +2 was probably fair, but the frequency with which players use the tactic doesn't warrant too much heartburn over the inconsistency. I'm all for being consistent, but I'm not going to lose sleep over some things. Now, if a player happens to remember the prior ruling (which is possible given that they're managing tactics for one character vs. the whole world) and says something (strangely, I've never had a player remind me when I ruled it +1 the first time and +2, later). There are three ways I might handle that: 1) They say it as a friendly aside and it makes sense to me. -- OK. Cool. Let's go with that. 2) They say it as a friendly aside and I think I might have gotten it wrong last time. -- Let's run with that, but note that I may change my ruling next time. I'm not entirely comfortable with my previous ruling, but I don't want to screw with you guys. 3) They pull a "gotcha" and get in my face about it. -- Don't be a dick. My current ruling stands, for now, and we can discuss after the game. (This rarely happens, but it has. I have zero tolerance for adversarial play. The GM is not the enemy of the players and the players aren't trying to beat the GM.)
Also, this isn't a slam on you, but literally every single DM who has ever told me that they reward players for "cinematic" gameplay has killed my characters when they tried to do anything cinematic (usually trying to drop on monsters from above and plunging my sword into them). Often by suddenly and thoroughly applying all of the rules (at least the ones that grant negative modifiers) and forcing multiple difficult rolls to succeed. The term "cinematic" is extremely vague, and my experience is that many DM's say "cinematic" when they mean "I will let you do really cool, amazing things, but only when I consider it dramatically appropriate and in line with how I imagine this story playing out, but if you try to do anything amazing and cool that disrupts my pre-planned storyline, I WILL KILL YOU DEAD."
Do not conflate "cinematic and cool" with "dance for me". I meant it much more in the vein of letting the character be who the player meant them to be. No one creates a swashbuckler with the image of them standing toe-to-toe with an ogre, trading blows. They created a character who is supposed to be agile, skilled, and able to turn urban terrain to their advantage. That's not
my intent, it's the
player's -- yes, there's a bit of assumption, on my part, but I don't think it's unreasonable assumption. Other archetypes have their own "cinematic and cool" schticks. If the tank starts climbing on tables, that's when I'm going to start thinking about wanting an acrobatics check to get on the table -- probably low enough DC that the swashbuckler can ignore it.
On the other hand -- and here's where we may have to agree to disagree -- I don't want a miniatures skirmish game. I love getting my tape measure out, moving stands of troops across a 15' x 10' block of painted terrain, and marking the damage off with pipe-cleaners. I will happily spend a weekend doing that. I've also been loving Gloomhaven and enjoy games like Mice and Mystics. I've also put several hundred hours into just Fallout 4. That's not the itch I'm scratching with an RPG. RPGs are open-world games and I play them, instead of those other games, specifically because you can go beyond the books or machine expects. If you expect me to go with "just the RAW", I might as well go with one of those others.
That's not to say that it's badwrongfun to do a dungeon crawl and just kill stuff. There's a bit more "tactile" something in doing a D&D dungeon crawl than even something like Gloomhaven. That's just not what I'm interested in. If it's what you want, then we should probably not play at the same table -- but it should be without malice.
I'm very, very up front with the sort of game I want to play. I
don't want some artsy LARP-wannabe or to write (perform) a screen play for a small audience. I actually want to engage in a
game. I just want one that takes advantage of the human creativity, ability to handle curve balls, and tell stories. As I've heard it put on one podcast, "If you want to write a novel, go pour yourself a glass of Scotch and sit your butt in front of a typewriter. We're here to play a game."
I avoid railroads. That's the actual reason I avoid modules; if you start coloring outside the lines, you may as well put the book up. Typically, I'll throw a battery of plot hooks at the PCs and see what floats their boat. Once they bite on one, that's when I put flesh on the bones. I'm more likely to maliciously kill a PC because they're waiting for me to tell them what to do than because they went "off script". (Actually, I wouldn't kill them. I'd just mentally slot them as an NPC under another person's control. Play will follow those who are self-motivating.)
If I wanted to put my thumb on players, I certainly wouldn't be suggesting a game like Fate that builds into the system ways for the players to directly changes the narrative and works to create games that are by group consensus. I just don't want to sweat the small stuff.
When I hear a player say they want just RAW and the GM shouldn't make rulings, I get scared that the player is going to be antagonistic and that, if I do misremember a rule or have to fill in a gap not covered, they're going to jump all over it and try to rules lawyer things. And, should I do some sort of world building (which I love), and tweak a rule for flavor or omit their favorite race because I couldn't find a niche for it, they're going to argue about it being in the RAW and that I'm a bad GM for actually spending time to create an actual setting with enough back story to hang a plot hook or character motivation on, rather than an amorphous blob of rules bits. Part of that is experience, but a lot of it is from spending time on these forums and seeing what folks say about GMs who would dare limit player choice within a setting. So, when players say "GMs should run by RAW," what I actually hear is, "I will do my level best to control the game, the GM, and the other players by beating them into submission with rules arguments."