MarsSeed mentioned that it doesn't make sense to have this package, but I have a few points.
First of all, the "next" branch in fdev31's picom fork was actually updated in March, while the animations-pr branch (the branch used in picom-simpleanims-git) was updated in April. The two branches were updated just one month apart, which really isn't enough to say that "fdev31 is working in other branches, not in the 'next' branch."
Secondly, I wanted to highlight a weird bug in the upstream "next" branch by FT-Labs concerning the displaying of shadows on right-click menus, at least on the window managers I have tested it on. I have found that this particular branch of fdev31's fork does not have this issue after testing it on a few window managers. It is somewhat hard to explain, so I can try to send a video if it would help.
Considering that the upstream branch has a few bugs and the branch my package uses isn't unmaintained, I think my package isn't really useless.