Hello Xaverus,
I am a returning player. I came back last spring. Apparently it had been 7 years since I was last online! I have really enjoyed WoW since then but one of the things I was missing was the social aspect of a Guild. I joined a guild for this xpac that I am very happy with at Tryhardish.
There is a wide variety of experience levels that lead to a more casual atmosphere. But, the officer team is knowledgeable and skilled while being dedicated to forming a positive environment. Avg age is probably in the mid 30s with a ton of working adults that want to game.
We were focused on recruiting for a raid team recently and now have one going. We are currenting finding new members to run M+s, do some delves, or to rotate into raids if desired. There is a handful of skilled players looking to run keys and also another group of players interested to start. I fall into that second category :). We normally have one or two M+ teams rolling around in an average night as long as its not raid night.
If that sounds like it might be a good fit for you, I invite you to check them out. Cheers,