I think this helps to explain how a particularly enshittified page loads OK, but if you don't close that tab before you move on, it can be trouble later on. Even if you add a number of lightweight tabs and everything is fine when clicking between them, clicking back on the "overloaded" tab tips the balance so much more than it should, that everything freezes.
It surprised me quite a bit that so many resources were being used even though Firefox is not in focus. It makes sense from the browser perspective, though, since you don't want to completely stop a web app when tabbing away. Almost all CPU usage is the result of the active website's design.
It actually made it appreciative of how Firefox uses almost no CPU "passively", and I'm curious if the same thing would be true for Chrome. If you discount memory usage, the browser is surprisingly lightweight.
That being said, have you looked into something like this:
https://addons.mozilla.org/en-US/firefox/addon/auto-tab-disc...
(Disclaimer: have never used it, but it is a recommended extension). It may not meet your needs exactly since it would likely reload YouTube tabs when "undiscarded", but it might be worth a look.
> I've always been a bookmark guy, and I don't know how you hundreds-of-tabs guys do it.
I use both. I use a modified version of TabsAside, but I also use multiple windows, one for each topic + general. The way I work, as I go through the relevant material for the current topic, I open new tabs in the background (to research later) so I don't interrupt my flow. Bookmarks are too much friction for this workflow.
I can't figure out why Google needs 15X more CPU indefinitely to display a white page with a search box, though (compared to a blank tab or simple site).
And with some news and minimalistic blog sites, one would be led to think the clean design points to a lack of bloat, but nope.
I don't doubt that Facebook is a hellscape when actually in the web app, though.