Yes, that's an opinion, but it's one that's very widely shared.
Why do Compounds make the game less fun? Because they are too difficult relative to the other Adventures at the same level. The result is that players wait at the elevator for the gate to change, or will often just run through the Compounds.
What makes them so difficult? The multitudes of small ground monsters. There are too many, and they are too invulnerable/fast/annoying.
If you are solo and the final room has the two keys with gates, it's nearly impossible to slog thru the multitudes of ground monsters.
In summary, Compounds make them game less fun because they are too hard in their current form compared to other more doable and more rewarding Adventures at the same level. The number of ground monsters needs to be reduced, especially relative to the number of players on a party. Also, the frequency of appearance of Compounds is too high. Finally, Compounds need to be more rewarding in terms of pickups.
Compound is, complicated compound often come with some nasty mob combinations, ie, fiend + mini slimes. Can be death taps for noobs.
Bombs are still not good compound is often said to be good place to use bombs, but bombs and bomber gears are still underpowered. Makes crafting compound specialist gears not worth it.
Risk vs. Reward compound don't offer enough treasure boxes to incentivize the players to grind through them. With only around 4~6 boxes. I am better off stand up to stretch and wait for the next level to rotate.