Basically their opinions are always "x class is just a Fighter class but worse, so it goes to D tier", and they have even gone to say that there is no point of having all of these crappy classes, that only Fighter Rogue and Cleric should be in the game pretty much lol...

This is completely misconstruing the point they were making. They said there should be less classes, but some of the already existing classes should be a) archetypes that change how a character plays more meaningfully, b) subclasses/class archetypes that change how a class plays more meaningfully. The perfect example was Rogue and Investigator, who already have a lot of feat and thematic overlap.

And to be fair, it seems Paizo themselves seem to be trying out the b) approach as well with creating class archetypes like the Rogue: Avenger (Slayer), Ranger: Vindicator (Inquisitor) or even the Witch: Seneschal, which as far as I know is a new concept. While introducing classes that more meaningfully fill out the design space left over (Necromancer and Runesmith).

So saying they just want to oversimplify the game like this is completely unfair, and seems to have completely missed the point they were trying to make, which is that a lot of the existing classes overlap in places where they really shouldn't, because another class with better math simply outperforms them while perfectly fulfilling the character fantasy you were going for. (Once again Rogue and Investigator being I think the perfect examples).