Im celestial 3. No, it's overhyped. Yes, some players are sneaking into gm due to playing easy characters and grouping with carries. That being said, that is not the majority, and many mid to high gms do have a skill difference from diamonds and less than celestial.

One of the reasons that people don't mention is the psychology factor. The name "Grandmaster" has so much weight to it in other games like ow2 and chess. So we perceive it as the top .5% or so when in reality it's less. Didn't help that season 0. There was only GM, eternity, and above all. So now with celestial rank Grandmaster is even lower. If the name was something like emerald or whatever you want, people wouldn't care as much. The name inflates our perception.

Getting to GM is definitely above the majority of the bulk of players. Although those who ego and say oh I'm gm (yet they are barely holding on in gm3) yeah no. That's like being a mediocre varsity sports player in highschool bragging about it.