I've just breathed new live into an old tablet that, because of all the Samsung Bloatware + system app updates was 95+% full all the time even though it only had something like 4 apps I actually installed and used, by replacing its factory Android with LineageOS.

Now, I have an EE Degree and 25 years experience in developing software, including years of Android.

It still took me researching how to do it over the course of two weeks and actually doing it took me 4 hours and was a massive PITA (I literally had to re-install the factory OS just to toggle the "Allow OEM unlocking" option because my first LineageOS installation that looked fine actually went into a boot-loop on first restart), though the result was well worth it.

(BUT, the version of LineageOS I have has a stupid bug and if I wanted to upgrade it to fix it I would have to compile LineageOS myself for my device, since it's not officially supported - and I used somebody else's precompiled binary - and I'm not sure if I have the time and patience for it).

This is me with all my experience in related domains and who actually did something similar for my brand new phone a few months ago.

Absolutelly, if you are lucky, have the exact right model, somebody else on the Internet did all the work for you in a nice video, the files you needed hadn't yet dissapeared from whatever file sharing cloud storage *#%$ they were place in, and you are technologically inclined, it shouldn't be too hard.

On the other hand, the average person out there doesn't have the technical expertise to even begin to understand what's going on and the whole thing would fail on something as basic as not having the right USB drivers on their computer.

All this to say that your expectation about what people in general are capable of doing is wildly of the mark.