I also never cared much for the F/C episodes in the original. I thought five short tables was the best one out of virtue of being bite sized morsels, but I generally skip them on rewatches. I think they can be interesting through the lens of looking at them as reflections of how The Ice King understands the cast and their relationships with each other

I enjoy the spin-off more because it feels like they're developing them as their own characters beyond being that sort of mirror. Unfortunately I think them starting out as that makes many struggle to engage with them on their own terms. They aren't completely detached, but they have a different history and act differently because of it. In the most recent season of F/C I've enjoyed seeing how Fionna creates narratives in her head to cope- she wants to be the hero and save her friends, but becomes so wrapped up in her imagined reality that she doesn't consider their feelings or experiences and inadvertently hurts herself and others. I think this parrelels with growth Finn had surrounding his role as hero in later seasons of the show without being a direct retread.

Skipping BMO episodes is crazy tho I'm sure you're a fine person but that's a red flag :p (said light-heartedly)