I think Bowser is being criminally underrated because of heavyweight stigma and the fact he's one-dimensional. His neutral may only be jab and grab, but it's still good because he has burst to cover every defensive option.
It's kind of disheartening playing DK knowing I could just play Bowser and do the same thing with less effort. I'm struggling to think of an MU that DK does better in.
Disclaimer: I don't play Bowser, so I'm only going off observations of some Bowsers I watch like Rafa, Ash, Le Troof, Ho3King (something like that) and a few others.
Heavyweight stigma? As if people inherently hate fat boys just to hate?
I assume you mean the fact that the heavies get to ride the combo train and ultimately have poor vertical anti juggling strats? That's true.
Admitting to a character's "flatness" means that if put in situation where your tools aren't as important as usual or nulled, means doom and gloom. I often times see Bowsers go for jab or wait for rolls to do an up b punish in neutral and I say, is there more? Now I'm no Bowser expert nor will I claim to ever be one, but having one plan and one plan only seems a bit narrow minded for a character.
What do you mean playing DK and Bowser is kinda disheartening? DK with his larger air mobility and less ending lag on key moves (uair, bair, dtilt, utilt, giant punch) means he has more at his disposal to rack percents and kill while if Bowser gets out of Shell Shock percents, fthrow and bthrow becomes life (probably more options, but I don't really notice them cuz you know, not my type of dude).
Some MUs that DK does better:
Mario and Luigi as DK has just as an easy time racking percent and killing them and his tilts really can void landing aerials and DK up b really screws with Mario dair.
Ness. Boy this MU can be stupid easy if love to capitalize on being greedy. If they go for dthrow fair to uair, you can up b the uair and get 36 free percent. DK has enough in his arsenal to make Ness play less of his game with bair and utilt royally hurting his air game. While Ness's big dome hurts people, don't forget that DK has one too. FOW even thought it was a rough MU.
Sheik. I ain't saying he wins the MU, that's ludicrous, but what I'm saying he does better than Bowser in the MU. On stage, DK has strong options to cover Sheik tactics with his impressive tilt range and bair. Where the MU turns to poop and may go into Bowser favor is the ledge. DK has easily the WORST options off ledge. Exposed hurt box, slow roll, slow ledge attack, slow jump, no aerials and only ledge getup is OK, but it predictable. Otherwise, still a closer than expected MU.
Cloud. This may be personal experience speaking volumes over the masses, but I don't think this MU is cancer, in fact is hella fun. Having 4 Clouds in my region and almost beating Ally's cloud at Landlocked makes me confident that this MU is even at worst. Sure DK gets juggled by uair, but who doesn't? DK can also make landing as cloud tough as utilt outranges dair and his hands are intangible too. Ding Dong is flexible and he has no trouble killing without it.
There are more MU that come to mind, but I would rather see retort before I decide to go farther. Plus typing all this at once is kinda annoying on a phone.