I read about "how much Crap there is in windows" and thought linux should be much smoother to run on my laptop. But it turns out to be the opposite. Firefox for windows works much better than Firefox for linux. For me windows just works. Linux even without telemetry struggles to perform as good as windows.
Hmm, I'm not sure then, there must be something more to this.
Within the distros you tried have you used Puppy as well? Just for the sake of seeing a very low requirements system running and checking how that performs
Linux even without telemetry struggles to perform as good as windows.
This is not normal. Even Xubuntu (with snaps and all) brought back a Core Duo (not a Core 2 Duo), which is EOL as of 13 or so years ago now.
Windows 10 was barfing all over itself and the mouse would take a good 20 seconds to make it across the screen. With Linux you wouldn't be able to tell the system was older than a couple years. Sure, programs took a bit extra to load, but once they did it was really smooth. I knew it would be better, but it worked fantastically.
The person using that system has been using it since the beginning of the pandemic to work remotely. I keep asking once in a while to see how it's going and each time they say it's working great. No errors, no issues, no slowdowns, just does its job.
I've put Linux on a few computers over summer. Actually, I put Debian on a few computers, but I tried a few different desktop environments. Debian internally works fine for my needs, and IMO it's kinda a "low drama" OS. So on my 4-year-old laptop and 7-year-old gaming PC, I used KDE Plasma, and on my 15-year-old PC I used LXQT, which is considered lightweight, after trying a number of options. The laptop has NVidia graphics and the 15-year-old PC has some janky GeForce integrated graphics, so I have gotten stuff to work with NVidia. Debian in particular has a really straightforward guide on the wiki on how to install graphics drivers.
I use Librewolf (Firefox derivative) on most of my Linux PCs, but Firefox ESR (extended support release, bundled with Debian by default) performed fine on the two newer computers. It's a bit sluggish on the older one, but fit for purpose.
There are probably compelling reasons to go with a distro other than Debian, but IMO Debian works great for me almost 100% of the time for a few different use cases. It's probably not the best OS for everyone, but I do think it's "pretty good" for most people. It'll get the job done.
But more importantly, there's a Linux distro for every niche. There are lots of lightweight distros with old PCs in mind that are much faster than even old versions of Windows. If your computer somehow can't deal with a desktop environment, a window manager like Fluxbox will work great.
Well it may not be cpu performance that firefox struggles with on linux. There is a Touchpad Scrolling Bug for firefox on wayland, that neither GTK nor firefox want to fix (if I remember correctly).
There are some more things like that, that suggest Firefox team focuses more on Firefox for windows than Firefox for linux.