For the time being, I agree with you on Pillowort. I've heard it's really slow because it isn't prepared for this amount of people joining because of the Tumblr purge, and I don't think the hype for it will last.
Maybe when fandom finally decides to settle for another option and when Tumblr keeps doing more shit like this (which I don't doubt they will), in a few years, as you say, people will abandon it.