It can still work well enough when developers don’t go crazy with divs, and when they use shouldComponentUpdate. But nobody uses that stuff; and modern pages are bloated like crazy.

For my money I think the problem is cultural. Theres a community and culture around frontend engineering now which seems to entirely disregard performance to the throne of closing tickets as fast as possible. Lots of frontend devs I meet at conferences and meet ups have no idea how the browser works, and no real desire to learn. The result is disasters like the new reddit homepage - which needs more horsepower to render smoothly than AAA video games did a few years ago.

The GP is right. There’s an insane amount of performance being left on the table. I don’t think it’s a technical problem. It’s a cultural problem.