Why do you assume it is the browser's fault? I use firefox in desktop and mobile and i can do everything you described.
A more productive approach would be to ask: What can be preventing me from doing or accessing X?
Then people could make questions and try to pinpoint what is causing the issue.
There are so many things that can cause issues like that, for example, in the browser privacy section of settings you have 3 options for cookies: standard, strict, and custom.
If you have "strict" selected, the browser will block necessary cookies for some sites, which can then cause numerous difficulties, im no expert on this, but i know because i have selected that option in the past and that has happened.
This is one of the most obvious things, but there are others that people can point out.
Even chrome can start to cause you the exact same problems depending on the configurations/options selected.
But to keep this productive and useful i would say you could try to create a new profile, while keeping the old one, and see if anything changes when browsing from the new one.
Are you really suggesting the browser has become worse over time? That is has improved in such a way to prevent you from browsing? It doesn't make much sense does it?
