I think a big problem is the fact that many web frameworks allow you to write these kind of complex apps that just "work" but performance is often not included in the equation

so it looks fine during basic testing but it scales really bad.

like for example claude/openAI web UIs, they at first would literally lag so bad because they'd just use simple updating mechanisms which would re-render the entire conversation history every time the new response text was updated

and with those console UIs, one thing that might be happening is that it's basically multiple webapps layered (per team/component/product) and they all load the same stuff multiple times etc...