For the sharpshooter feat, there is a big difference between your archer line archer and robin hood. With the max 20 stats the value of feats grows quickly. Sure taking +2 dex for extra damage and to hit is nice, but looking at best doing that twice before your dex is maxed, assuming your not rolling stats and start with 20 dex from race mods. If there wasn't the 20 max stat I might agree that not having feats might make sense, but with 20 max even with two main stats needing more than 4 stat increases is rare as any other stat increases have significant less meaning.
Feat for different arrows? doesn't make any sense, any archer could drop any arrow into a bow and shoot it.
taking -5 to hit is a huge penalty and personally is never worth it, as missing nets 0 damage. The option is a high risk high reward option. People singing the praises of the feats that give this are people who like to gamble if you ask me. Probability doesn't mean much if the dice don't feel like rolling in your favor. In the LFR games i've played in, a 17 is a common minimum to hit things, trying to land a 17 with a -5 penalty is a long shot, for a champion its almost the same as their crit range at high levels. When it does happen it's awesome, but in general you are likely to net more damage done without it. The chance to attack again when you crit or kill on the other hand is amazing and worth the feat by itself if you don't have another way to use bonus action to attack.
Just to toss in a little cheese, sharpshooter and crossbow expert are useful for a rogue who wants to apply sneak attack damage when attacking with a net. pretty sure weapon master is also required, or a level of something that gives martial weapon prof. Without feats, the net is basically useless.
Crossbow mastery for me is taken more for the not taking disadvantage when attacking in melee, in some cases for the extra attack with a hand crossbow. In many cases the loading property doesn't change combat patterns.
I would say that feats add complexity not remove it, as they add tweaks and options and reasons to use certain features. Like charger, without it charging doesn't exist anymore.
Saying that feats don't add versatility and that +2 stats is always better doesn't make any sense. Feats like medium armor master are better than +2 to a stat, especially since if your taking it your dex is 16 or better already. Of the defensive duelist letting you add your prof mod to your AC when you have a finesse weapon. No +2 stat is going to let you character have two cantrips and a first level spell. +2 stats won't let you do ranged attacks in melee range of an enemy without disadvantage. +2 isn't going to give you superiority dice and skills. +2 dice isn't going to let you gain proficiency with weapons, armor, or skills. I could go on.
Back to GWM, said fighter is only better than other fighters who are also using great weapons. Without a certain list of weapons the feat is useless. It is a niche choice, granted the niche is pretty big, but still niche. That is kinda the point of the feat, instead of being good with great weapons you are a master of them, masters are typically better than non masters. Also, with so many stat increases, what else are you going to do other than pick up feats? Feats are kind of the focus of fighters. if you just take stats that is +14 points, with a 20 point cap, most of those stats are kinda wasted as a fighter. It's kinda nice having higher saves on the mental stats, but ultimately those points are pretty wasted in most cases, and also just don't make any sense in many cases too. Getting hit in the head for a living isn't very conducive to having high mental stats. Focusing on great weapons makes you almost useless in skill challenges, almost useless in puzzles, and almost useless if some one decides to use the disarm or grapple action on you. In specializing in that manner you are opening up more and more counter play. In the example of "horizontal" feats, those feats are vertical feats, having the actor feat gives a vertical increase in skill challenges. Ritual caster gives you a vertical increase in magic use, and depending on the ritual can do some really cool things that other fighters can't do. All the feats act as vertical power increases, just in different areas. In some cases +2 in a stat is vertically better, in other's it isn't. That is kind of the point of choices. Again with a 20 point maximum on stats, there is only so many meaningful stat increases before its a waste, or at best subobtimal for the character design. Say I'm making a beat stick who does nothing but smash face in, after one or two +2 increases into STR, stat increases won't let me smash face any better, this is the same for any character that wants to specialize. Feats giving the only option to specialize after you run out of stats to increase. Must have feats only apply to specialists. If your not specializing, than nothing is must have. If you are then anything in your area of expertise is a must have, including stat increases.
Maneuvers like spells for martial classes, so 4e?
The classes are general guidelines, and the sub classes give more depth to those guidelines, feats are something to help solidify the identity of your character along with backgrounds. The option to not take feats is still there, just as the option to take feats that give a broader scope to the character and make them more of a generalist, these all make it so if you are wanting to play a generalist your options aren't limited to bards or rangers. You can make an arcane fighter that knows divine magic and likes to sneak around every where and knows how to get what they want. And be pretty decent at doing all of them. On the other hand the option to hyper specialize into one and only one thing is there too, and everything in between. You can even make a character that isn't really good at anything.
Who is to determine right and wrong? well math is a decent place to start. Science is also a good option. In 5e, there isn't really a right or wrong, there is character diversity, what do you want the character to be and why. That is the state of 5e. Are some things subobtimal? Only for specialists, for general characters who want to be decent at everything instead of really good at one or two things it's hard to be sub optimal. Back to the -5/+10, normal encounters in LFR games require reliably hitting a 17 to do any real damage, with a -5 to hit, this isn't going to happen and -5/+10 is a bad choice for those wanting to specialize in smashing in faces. So no encounter is being skewed just for that option, and it isn't much of a skewing really, hitting a 17 with +5 means a 12, +7 for archers is a 10, 1st level characters usually have +5 for melee and spells, and +7 for ranged. taking neg five to hit a 17 means those melee now need a 17 on the die to hit, those archers need a 15 on the die. statistically that is a -20% chance to hit for a damage increase of between 50-100% When the chance to miss is already greater than 50%. I dont see why a 30% hit rate for double damage is a good idea. Missing once means your netting the same damage as if you hit twice normally. The number of times where a -5 would have made me miss an attack generally ends up every attack i hit with that isn't a crit. -5/+10 is a trap. Cool when it works, but unreliable at best.
A group of specialist isn't better than a group of generalists in 5e, as skill challenges are a thing. When you succeed of fail as a group having a couple of people that are too focused and can't help in the challenge can be the lynch pin that makes the group fail the challenge. 5e isn't all about smashing in faces like 4e was. and back to -5/+10 Only an idiot uses this on every attack, it is best used again low armored targets that you have advantage on and other wise ignored completely. Why are people so quick to dismiss the pain of -5 to hit. Also why are people so quick to dismiss the power of utility? Martial adept, one of the options is the chance to trip, giving every melee attack until that creature acts advantage, another lets them shove 15 ft, which can give instant kills when they fly off cliffs or into pits or the like, and all sorts of other creative ways to give massive power to the user or it's party. Actor gives you more power in social skill challenges, which are very important for getting extra gold and xp and other interesting things like contacts and favors and letting you slip past guards to not have to fight at all. As for ritual caster, take a look at the ritual spells and try to tell me that isn't some awesome power.
In 5e having a party of good across the board characters than a bunch of hyper specialized characters. As a hyper specialized party will either have one person good at each thing, and that one person does everything when that one thing comes up, or will have a gap where no one can do one thing, and the DM punished you and makes every adventure all about that one thing. It's nice having one character that can shred the hp of enemies, but they have to keep in mind that they have to either skill and or feat up to be able to handle other situations, or that when those situations come up they will have to sit and twiddle their thumbs and not do anything. It's all about give and take, risk vs reward, and making a character, not a stat stick. People have things they are good at and things that they are not as good at, i've seen many people look only at the stats and not take into consideration of who the character is and why they do what they do.
Wow thats a long post, and i likely repeated myself a few times...guess that happens when you reply to four pages of post at once.