This is a bizarre take, as most jj users just take your paragraph above and do a s/jj/git.
The benefit most people find in jj is that you can do stuff easily without having to think much.
There is no separate concept for stash and index (and yet you still have them in jj, and use them without giving them special names).
In principle, there's no real distinction between merge and commit.
You don't need to know the difference with/without --hard for git reset. You just do a "jj undo" no matter what.
Merge conflicts are not stress inducing. And if you're in the middle of an ugly merge conflict, you can just say "Screw it all" and quickly get back to before you did the rebase/merge - just keep hitting "undo" until you get there.
jj literally has a much smaller cognitive overhead than git does.
That said: you should use the tools you like to use.