Playing some DKC3 since it dropped on SNES online (first time I play the SNES version). The game is often memed as a "black sheep" of the series and I don't think it's quite correct to call it that: most people that played it seem to like it beside the occasional Kiddy Kong jokes, and it was still a solid seller despite being a late release. But certainly most Kondey Dong people don't seems to feel about it *as* strongly as they do about its two predecessor, and beyond the oft-cited reasons (soundtrack, tone/setting, kiddy kong), I wonder if there isn't something more subtle at play, the "You didn't notice it, but your brain did" factor, the reason the game is often dimissed as "too gimmicky" (despite both previous games having a lot of "gimmicks" in their levels)...
... And that's the level design. In an interview, Gregg Mayles said he was inspired by SMB3 and they made DKC levels so that you could just muscle them with minimal interruptions if you were half-competent at plaformers. That much is obvious when playing it and DKC2 is also like that. DKC3 isn't, there's a lot of levels that can only be speedrunned (the seesaw, bees) and a lot more that require a lot of start-and-stop gameplay (hanging onto levers to unlock door) or backtracking to pick up objects (grabbibg barrels to kill rats as the elephant). Even when there isn't some such gimmick a level is built entirely around, levels don't seem to be build around the before-mentioned principle in mind, having a lot of instances where you can't just jump above or run under things and have to wait for an enemy to clear the way (apparently the GBA port deliberatly set out to fix this).
On the other hand, what makes DKC3 running and bopping less exciting makes the 103% quest more engaging: the more complex level gimmicks allow for more interesting bonus room barrels, Koin puzzles are more interesting that just scavenging the level for an arbitary collectable. The non-linear map and Brother Bear quest add a layer to the adventure beyond jumping on dudes (even if some of the overworld stuff, like the crystals, is dreadful). I'd be interested to see if there's a pattern on people's opinion on the game and if they're the "I just want to get to the ending credits" vs completionists type. .