So taking a 172cm snowboard (most likely more designed for big mountain riding) is not fun in the bumps, thats similar to saying 212+cm downhill skis suck in the bumps, yes, equiptment, and choice of equiptment, can and is a limiting factor, but you chose that equiptment for riding your preference in terrain, not necessarily for all-mountain riding/cruising and from the sounds of it, not for learning new things.
I have skis that are 90mm+ in the waist (quiet wide wasited for skis), and I can honestly say they scared me when I tried to ski the bumps with them, however, they are more design specific skis (designed for big mountain and park and pipe), not all mountain, does that mean I can't or shouldn't ski bumps, no it means my equiptment is a limitation, while it would be possible to ski bumps on them, my all mountain skis are better suited for bumps.
In terms of the fun factor, I hated, no, HATED bumps for years, and would avoid them at all costs, they weren't fun, they hurt my knees and lower back, and I never felt like I was in control. However I did not let that be a deterant for me, I wanted and desired to be able to ski the whole mountian comfortably, and bumps were always my limitation and anything but fun. However, once I realized how to ski them they became fun.
Trees are great practice for the bumps, often times trees are seen as an obstacle to turn around, much like bumps, but when you learn to look at the light spots (openings in the trees) and not the trees themselves you can start to utilize the trees to help establish a rhythm, much like the bumps. Furthermore, when you get into really tight trees, you need very quick reactions, and a totally different blend of your skills base than what you use on groomers, that ability to adapt your skills base is the same in bumps. Often times people have the skills needed to ski/board bumps, but don't realize it, which makes me say it is not typically the skills (rotary movements, balancing, edging, pressure control and being able to blend the 4 main skills) that need to change, but the mindset and approach.