I've had good results with the react-rails gem, basically letting me plop bits of react into a rails view. It's not like, the best the in the world from a pure design standpoint? But it does a really, really good job of not having react step on the toes of all the super nice things that Rails will do for you.

I think nowadays there are a lot of people that only built SPAs and never have used a framework such as Rails or Django, and that's a pity. They are missing a perfectly valid and productive way of shipping quality software.