That's an interesting question because I've gone over it multiple times in my head and I've played many different kinds. What makes MOBA's shitty is the communities you play with. It's great when you're on a team of people you know, but others can make it a pretty sad experience.
Essentially, I don't really like Dota 2 for that reason. It's also intimidating the Structure that Valve built to make sure that you're gonna spend money. LoL is Straight up Arena and easy to get into.
I also don't think there's enough people playing SMNC, that one is actually pretty great!
Eh.. Moba is a pretty niche thing, but there's a surprising number of ways that style is presented that might be cool to anybody.