So, I have an observation and a question stemming from it. By the way, feel free to tell me it's ridiculous if need be, maybe I'm just new....
Looking at this discussion there seems to be quite a bit of negativity towards the idea of more options in general when they're for the player, with some outright stating that this is one of the biggest ways to impact tables in a bad way. Why is that? I'm primarily a player myself, and don't really understand the hostility. I love making characters, mechanically and through narrative, and every time Wizards releases an expansion to character options my field of possible characters and experiences in 5E gets bigger and better. What's wrong with that? Has it always been this way?
Having played since BECMI and 1E, I'll give my thoughts (mostly as an AD&D GM). Assume everything is IME and IMO.
As the referee and rules arbiter, the DM needs to be comfortable with the rules being used at the table. In AD&D, this generally played out as the DM deciding which Dragon articles, rules supplements, and third-party products (Judges' Guild, etc.) to include. Most of the time, the DM would be the one buying all the stuff beyond the PHB, anyway. If you bought the other stuff, it was either because you fell in love with, say, the Alchemist class in a certain expansion or you wanted to DM.
Even for core "modules" like weapon speed factors or weapon vs. AC, the DM would decide whether to apply them or not. Most of the tweaks to core rules easily put into a couple of tables that could be shown to players, as needed -- I had a custom classes allowed and max level by race table, for example. These decisions were made, generally, to evoke a particular "feel" at the table or to address play issues (like rules lawyers and egregious min-maxers).
To an extent, this was even encouraged by the 1E rule books. The math behind the to-hit values was hidden in tables that were only available to the DM (well, they were in the DMG). The DMG was full of variant rules and secret effects, like potion miscibility and side-effects for various spells. Artifacts were listed with actual blanks for their powers so that the DM could fill these in as he chose. The DM was considered the ultimate authority and the only window to the game the players had. A good DM was one who was able to manage the rules in a way that challenged the
players in a fun and engaging way.
As an example, I had very mixed thoughts about 2E AD&D. I absolutely despised (and still do) the addition of TWF to the Ranger class, but loved the rules for Priests and the ability for Thieves to tweak their skill advancement. The game I ran was basically 1E that borrowed copiously from 2E as a supplement. The TWF Ranger remained banned all the way through the end of 2E (and, actually, even the 3E Ranger was banned -- the 3.5 Ranger was allowed, but TWF was not an option). There was absolutely zero argument -- or even consideration of argument -- about this. It was my table and that was the game I was running.
That doesn't mean there were no arguments about the game. Over 35ish years of being a GM, I've made a few really weird calls. It happens. Also, sometimes players see what's supposed to be an in-character plot hook about why things work different than expected as an out-of-character rules change. The point is that the arguments were rarely about whether I was following RAW. More often they were about what the rules should be at the table, with me being the final authority. The printed rules were either the base framework (core books) or resources to bolt on (and maybe tweak), as the DM chose.
Just a note on what that "final authority" looked like: I was rarely the only DM available. Usually, there were 2-4 other folks who were somewhere on the spectrum from "willing to DM" to "eager/prefer to DM". At any time my entire group could have decided I wasn't the DM anymore. For the 35 years I've gamed, I've been GM 70+% of the time -- even when I really, really didn't want to -- because I was able to entertain my players at least as well as others available, despite having a fairly strong opinion on the authority of the GM. I actually think that "final authority" is necessary to a coherent, fun game.