From enjoy most to least:
-Team Races: it's a good opportunity for mid teams to work together and earn a decent ranked monster (When the race matching pools do not suck)
-Progressive islands: with perfect collection one can get the old replicate at least for ranking. Like for this one, I am just going for ultrabot to save myself 1 breeding
-Breeding events: IF they are for old monster and the combo is reasonable can help rank some monsters. I do not enjoy breeding events for NEW monsters and haven't enjoyed them in a long time. Last breeding exclusive monster I got was Firyna. I didn't even bother after that. (Total exclusive breeding monsters I have are Shallinar, LauLau and 1 Firyna) none of the combos after that were worth the effort.
-Mazes: used to enjoy these the most, there was planning involved. I used to write guides for these, but now when they place keys near the end of paths anyway instead of junctions, and make it only obtainable through one path, it's just another form of progressive island that drags on forever. Moreover, none of the monsters are that worthy unranked, so i just save my gems to buy them later if i want them.
-72 hr challenge: waste of gold and food and time and bloats ur xp just to make it more impossible than last time. no thanks
Funny part, is when lab came out we were promised that events like these will have more rounds so you can rank your monster. But instead, what we got is: making even the first round more impossible. Way to go to make new monsters appealing! Why should I bother get a new monster, I can't rank for a long time or with more gems, when I have a ranked one?
Imo monsters in events should already be ranked to 110 or 105 at least.
The lab killed the game for me a long time ago and it only became worse and worse.
So, all and all I think all event are horrible now and we are running out of reasons to even bother ^_^ I find myself playing less and less everyday, so kudos for that. I'll miss it way less when I eventually drop out this way.