A typical adventure module assumes the players won't play the adventure. And sadly this is both common and true.
[[Citation needed.]]
As some say, but not all.
You can find
someone to say anything you want. Whether or not
someone says something is hardly a mark of its truth. There's someone who says that the moon is made of green cheese. Are you more inclined to believe that that is so as a result?
As a DM that demands a lot of role playing (the acting kind), it really does not matter if the players do it good or bad. Sure good acting is great, but even bad acting is a thousand times better then the player just playing themselves as the character and saying mechanical rule things like a robot.
You were going quite well here until you descended into insulting people again. "Playing yourself as the character" is a perfectly valid approach to roleplay--and it does not, in any way,
require "saying mechanical rule things like a robot". Far from it, in fact--playing a character that is pretty close to your own self makes it
much easier to roleplay authentically, especially for inexperienced players.
To star with, I very much tell players to only only role play character they can role play. If you don't have the ability, then don't do it. Stay in your Lane.
And thus lock them down into never actually learning how. Sounds like a recipe for frustrated players and a GM who thinks players don't care about things. Not that I can really claim credit for such a prediction--you've explicitly said both things are true nearly all the time with your games. A self-fulfilling prophecy, actively manufacturing the conditions under which players will act out, get hammered down, and then nope out of there because you've given them zero reasons to believe you give two $#!+$ about them enjoying any part of the experience.
For the few, rare players that want to work at it and become better, I'm more then happy to work with them and teach them how to role play and act.
They aren't few and they aren't rare.
You just need to be less hostile to players. They need a
reason to try. Otherwise, they won't. It's a simple as that. You create the very conditions which produce the results you then complain about.
I give rewards for role playing, and this helps encourage players to role play, but also role play their ability scores.
Now this I find surprising. Doesn't that conflict with the idea of "Hard Fun"? You're giving players rewards for doing something anyone could do.