I just started playing WoW classic. People always ask me how I like it, seeing as I never played WoW before. I would describe it as not very fun, but incredibly addicting. I'd continue to elaborate but I have to go do some leatherworking...
BTW, the fun starts when they introduce PvP honor and battlegrounds. Other than that it's a true grindfest.
As for the OP topic, shrooms are great, got me out of depression during my late teens. No preparation or anything, just took some with friends and embraced it with positive curiousity.
If there's one game that does "not very fun (occasionally) but incredibly addicting" for me it's Old School Runescape. I started playing Runescape in 2006 and I still play in 2019 (with some breaks in between). I'm 21. That's most of my life.