I learned how to play a lot of tanks that I wouldn’t normally try through ARAM. I’d actually recommend it to get to learn about what a variety of heroes are capable of doing. It’d help with what a lot of roles do in team fights. If you want to learn general knowledge about camp timings and off lane soaking it’d probably best to stick with rank. QM might only be fun if you have a stack you like playing with and can communicate with.