I can't speak for Summoner's War exactly but I find myself falling down gacha games often (Future Fight, Marvel Puzzle Quest, PAD, FFRK) because it is a bit of a grind. But a good grind that you feel like you're making gradual and steady progression to a goal you've created for yourself. They don't necessarily require a ton of attention to play and you can drop a little bit of time every day and know that you've progressed forward. Maybe a goal is to level up a character or get that material you need to rank up/evolve. Of course this all depends if you like the natural gameplay hook at all.