GraphQL is well over a decade old. I'm not sure "tried and tested" is a meaningful contrast between the two approaches at this point, especially as it relates to API requests from the frontend. It's okay for people to choose REST just because they like it better, and/or aren't interested in learning something different.
I think I shipped my first production GraphQL server around this time 8 years ago, but by all accounts it was in use at Facebook a couple of years before it was opened up. So overall ~10 years old sounds right, though the released spec is a little different to the internal version that predates it.
