There is no powergaming. If getting a 16 in your prime stat is powergaming then every single person who has every played a human character is a powergamer.
No, it's not, because as a balancing factor for having more racial ASIs, the humans lack many other powers, so in effect almost no-one plays a non-variant human. As for variant humans with the feat, on the other hand, they are part of many builds because of the feat, which again goes to prove that it IS a power option.
Sure, those people are terrible people. You should never yell at another player for basically any reason except that you were rping a scene.
But it seems you have responded to bullies by simply removing as many choices from the player's hands as you reasonably could. Which doesn't stop bullies.
Actually, it does, 20 years experience on this has shown it in our groups. Although, by far, the best effect has been obtained by putting the reins of the game back into the DM's hands, which has also stopped the bullies from rules-lawyering. In both these respects, 5e is an absolute, total win.
Because bullies aren't stopped by preventing good players from making choices.
The devs disagree about what makes a good player: "To play D&D,
and to play it well, you don’t need to read all the rules, memorize every detail of the game, or master the fine art of rolling funny looking dice.
None of those things have any bearing on what’s best about the game."
For me, a good player is a player willing to play WITH the other players and not AGAINST them in any way, shape, or form, and this includes not wanting to be stronger than the others for any reason whatsoever.
Again, a variant human with a feat is highly optimized. Just rolling for stats and forcing people to pick optimized races doesn't remove optimization, it enforces it.
No one at our tables has ever been forced to play an optimised race, if there is even such a thing. Actually, we have very few humans at our table, even though we allow variant humans.
Sure, you might prevent a dwarven wizard from having a 16 INT and armor, but you've also guaranteed that people who choose to play a halfling wizard because they like the idea are open to being derided for making "the wrong choice".
And it's people who deride other players for making a halfling wizard who find themselves uncomfortable at our tables, as this is bullying, contrary to the intent of the game, and certainly not the mark of a good player.
None of the actual problematic behavior is being prevented by your choices.
Actually they are, again, 20 years of experience on this and we have none of the trouble that 3e created for us. I agree that the problems are not completely solved, as there are still people coming with the "builds", but not having fixed stats forces them to think about their choices and actually do their own work (rather than parroting online guides), and keeps the discrepancies to a minimum, enforcing much better play and ambiance for every one.