Doing that whilst grinding is probably the least best place to do it in as there’s really not much to commentate on.
I’ve made some of my best MMO friendships from just being in a party with them and sitting in a field while chatting and grinding. But that’s besides the point.
A low rate and slow EXP progression is something that challenges you to play smarter, not more.
Suddenly you put a lot of time into finding a way on how to optimize things or just exploring places, in the search of doing things more efficiently. During this search you are bound to make mistakes or run into incredible things that you would have never seen if you just had followed some intended path. You constantly question the permanent decisions you’ve made and try to think ahead on what to do after you’ve reached your next personal checkpoint (such as learning a new skill or being able to equip that weapon you’ve had in your inventory for a while now)
High exp rates coupled with NPCs that just hand you quests for leveling discourage you from doing these things.
"Why would I go anywhere else? I can level easily here. Why would I think about doing my build wrong? If I mess up I can just make a new character. “Why would I look forward to equipping some piece of trash weapon I have? I’m gonna replace it in 10 levels again anyways”
There are just things that are very precious to me and many other people that you simply can’t have in a MMO where you level at a rapid rate.
What may feel like monotony to you is quite the opposite for many others. For us getting leveled up many times in a short time is monotony, because we are never challenged to improve on the things we do. For us it feels boring to just follow a determined path like a train on the rail along with anyone else. And since anyone can just finish any quest alone there is no need for communicating with others either