Its not big frameworks making the web big/slow. Its...

Yes, its absolutely the big fucking frameworks. In most cases it is the actual literal use of the frameworks, but even that isn't the real problem. The real problem is deeper. You can call it second order consequences.

Its developers that cannot optimize and cannot program without something like React. If you took React away would you suddenly not be able to do your job at all? That's horrible problem to have. The result is a bunch of toxic defensive posturing by people who suddenly appear not qualified to do the work.

If you cannot dig deeper you certainly cannot optimize deeper. That makes the assumption you are actually measuring things and optimizing things in the first place, which many developers aren't. Again, if a given developer lacks the capabilities to dive deeper they may also lack the capabilities to measure things, as is quite common.