I say it does a bit of both.
Some of the funnest memories that I have ever had were on imageboards. Browsing really helped me remedy my loneliness during my teen and young adult years. It was nice to meet up with a group of dorks who shared the same interests as me, without any forum drama (or at least, much less of it due name-friendging/trip-friendging being discouraged) and normals. I learned so many things through imageboards too, and some of the funniest (and most fun) memories I have are from the boards.
But imageboards were also a double-edge sword for me. I believe they became an addiction for me, so instead of going out and communicating with the real world, I became a recluse who was addicted to anime and video games. Another this is that imageboards degraded my mental health. For example, I used to browse /pol/ (4chan and eventually 8chan) a lot for learning about history, (/his/frens were on /pol/ too so I didn't really bother visiting /his/) for the bantz, and for the HAPPENING threads. And while I did have fun, /pol/ made me extremely paranoid and depressed about the state of the world. Because of /pol/ (...and maybe /k/ too), I used be super paranoid of all the bad things that happen, and it made life more mentally draining for me. Politics is hell, so I stopped browsing /pol/ altogether, along with any other board that had doomposting or blackpill-posting all together. Doing that really improved my psyche. I still do come back for habbenings though.
So, Imageboards really helped me out in formulating my hobbies. But they also were very addicting to me-- I never accomplished anything because I was so consumed with browsing them. Nowadays I don't really browse imageboards like I used to, especially since 8chan is gone. But I still hang around the webring from time to time. Ever since I stopped browsing them so frequently, my mental health has improved, and my life is slowly getting back together. I'm finally dedicating my life to my hobbies more and doing the things that I want to do.
TL;DR: From my personal experience, imageboards are fun if you want to stay away from normalfriend communities and have a good time. May even learn something new from them. However, browsing an imageboard can be addicting and the content on them may stress you out.