Browser developer tools let you edit all of the client-side code for a website, and these days it's pretty common for bugs to be in the client-side js.
It's slow and buggy and awful to use on most Android phones for most of history. It sucks the CPU and battery while you're not using it and slows your whole phone down.
> hardly fair to say they're slow or poorly designed.
No it's completely fair and totally true. The Facebook apps are really badly designed and so are the websites.
Ah maybe that's what I'm missing- I don't use their app. The mobile website mostly works well for me. They removed messaging from it because they're jerks, but you can switch the desktop mode and it works.
> They removed messaging from it because they're jerks
That's another case of bad design. Intentionally making the webapp worse for you by removing perfectly good features so they can extract more $/user on average.
They make lots of money and the make very poorly designed and user hostile software.
Can you tell more, how did you "hot-patched" the code of website big as Linkedin?