Can't speak for today (since I don't have an iOS device at the moment) and I understand that some of these things were eventually added as options, but when I used an iPad 2 back in the day, some of the things I jailbroke it for:
Systemwide adblocking, non-Safari browser that wasn't artificially limited, ability to connect bluetooth mouse (mostly for when I used the iPad to remote into other computers), modified keyboard with a number row, file manager, some minor homescreen/launcher tweaks for usability, and one that allowed non-iPad apps to run at a higher resolution (at the time, non-universal apps would run in the old iPhone res, but scaled up instead of running at the higher, newer phone resolution).
I'm sure there were other little tweaks, but the main thing was that there weren't any decent Android or Windows tablet options at the time and while the iPad did many things quite well, there were all sorts of little quality of life things that I was just used to having. They weren't included in iOS and there was no way to (officially) change the launcher or keyboard or any of those other things.
It would have been quite nice to have other software repos besides just the App Store which didn't require me to exploit security flaws to use. Instead I just stopped buying iOS devices after that iPad.