I feel like this is a bad faith argument, even if its not meant to be. Just saying "There's an unlimited set of characters no matter how much is excluded because different personalities exist" isn't worth anything because RP personalities aren't worth much to begin with when it comes to significantly differentiating a character. If there's only a single class/race/build/ect., then Joe the Cowardly Fighter is exactly the same a Bob the Brave Fighter. The only difference is it takes longer for Joe to get into combat. Once the mechanics of the game start being applied, they are exactly the same.
I also feel that your experience might not be that widely shared. For example, I play in a game with a decent number of boundaries. One being that the Druid class is banned completely for in-game story reasons. Now, I'm very much a person who hates boundaries. I've convinced a DM to let me player an Awakened Maple Leaf that was named Lief Oakenbranch as an actual character for a year long campaign. But I'm also more than willing to work within boundaries as long as they are reasonable.
I had said it in a previous post of mine on the last page: But Limiting options becomes stifling once you are no longer able to effectively create your idea. And the key word is "effectively". For me, that's mechanical builds, cause I find the mechanics of a game to be far more fun, engaging, and interesting than RP. For others, that could be RP. But in either case, the line remains in the same place: The moment you can't effectively create what you set out to make, then its stifling.