1) A "footsoldier" dev has no choice in frameworks, and heavy frameworks with heavy reusable components are the norm. Frameworks are used to improve dev velocity and ensure consistency among the 100 teams that contribute to the web UI.
2) Devs care about performance but might not have time to do much about it given competing priorities. Cloud is a fast-moving area, so new features are being added all the time. Even if they want to improve performance, they're limited by the frameworks you have to use.
3) For folks that are saying Google controls the browser, framework, and component library, and so should be able to do better than this, you are right. But the different divisions don't talk to each other as much as you'd think. Why should they? Angular devs shouldn't get special access compared to React, no? Whether this is an organizational failure or an enforcement of separation of concerns is up to you. I imagine critics will complain if Chrome did something special for Google properties, and they'd be justified.