> It already favours players who play obsessively.
This is the reason I generally stick to games with good single player campaigns. On rare occasions I'll play multiplayer with friends. But I think the last online multiplayer game I played with strangers was Left 4 Dead. I was always either booted from the game early on because I didn't play "correctly" or I received a "guided tour" by someone who had put 1000 hours into it. Just playing the game wasn't really an option, apparently.
I agree with the sibling that favoring obsessive players is par for the course with MMOs (or those who spend the most $$, which I refuse to do).
That said, I'm playing Pokemon GO (at nearly 40 years old) because it's just fun to collect the Pokemon, level up, and socialize with other players. I really don't care about taking over a gym. I can play this without competing with those people who have 40 hours a week to throw away on it. My social group largely seems to feel the same way, although a few are obsessive. And while I'm fairly active already, it has encouraged me to be more active.
As for whether it's a fad, it might be. Normally with free-to-play games I lose interest as soon as it becomes ridiculously difficult to rank up. With this, I think I'll start to lose interest when the rest of my social group loses interest. I think, for me, Pokemon Go is more likely to be replaced by something similar than just abandon out of lack of interest, though.