I could not possibly disagree more. I knew someone who all through 3/3.5 ran campaigns strictly off of the PHB, DMG, and Monster Manual. He ran them very effectively, and had fun campaigns.
In the general sense, I do not accept arguments in the vein of 'if you think something is imperfect, it's probably not for you and you shouldn't try to enjoy it, much less improve it'. Trying to improve the things you like and make them even better, for yourself and maybe for others, is something which can only serve as a positive. If someone disagrees, they can just not use whatever solution you found to make it right for you.
In the particular sense, I reject the idea that additive, optional content being released for a game can make it worse. You can Always just ignore it and play things as they were before the optional content was added. 5e is the same as it was before Tasha's came out, if you choose not to use it. You can just take the things you like from that optional content, leave the rest, or leave it all entirely, so ultimately whatever form of play you choose to engage in after that content comes out should only ever be as good as it was, or even better. If it's worse, then that's on you, and you just need to make better choices about what you do and don't allow.