Beast Mastery if more mobile than MM and are able to deal damage while moving (unlike MM). It has high damage and is a relatively easy spec to play. Currently, MM doesn't have any strong benefits. It is less powerful than BM even in ideal situations. Because its mobility is limited, it will only lose damage in situations where you have to move. Unlike BM, MM doesn't rely on its pet to do the majority of damage. Pets are bound to specific specs (Tenacity, Ferocity, and Cunning), but they all the same health, durability, and damage. Specific pets may be more useful in certain situations, but the only time that would matter is when you're in Mythic+ or Raiding. Once you're 120 and get some decent gear, it just comes down to whichever pet is your favorite.
I would give raiding a shot in BfA. It was pretty good in Legion and that will hopefully continue into the new xpac.
I still find it fun, but like what Xota said, it is subjective. We may find WoW fun, but you may not. The best way to decide if you really want to come back is to return for a time.