What I'm getting at is Bowser can not approach and has a terrible neutral game. Any player that knows to simply wait and bait Bowser already puts the odds overwhelmingly in their favor. Bowser can hardly punish whiffed moves, and his best option is to simply hope you can call out someone's weak aerial or whatever with DA. Flame breath can't convert into anything. Unless you have really good positioning, upB OoS can only reset the situation. Maybe you can UpB OoS to 200% and close out the stock with that...
Like yeah you can crawl/crouch forward to negate the effect of weaker aerials up to a point, but the more damage you have the less this is effective. Plus it's super slow so it's not like your opponent doesn't have all the time in the world to react to it and adapt their strategy. At high percents, the crouch/crawl armor is completely useless.
Bowser wins when you come at him inefficiently, and he wins pretty hard in those cases which can lead to the misconception that Bowser is pretty good. Yeah his combo game is pretty good, although he doesn't necessarily string long combos but they do their job very well, his edgeguarding is stellar and his kill potential is off the charts. But he is held back by the simple fact that putting any of this into use requires either a strong prediction of your opponent or someone mistakenly rushing in or not playing the MU right. Without any of that, you're going to have the worse time of your life struggling to land anything on a competent Falcon/Fox/Falco/anybody with a strong neutral, no matter how many years you spend practicing the 108 guaranteed methods of edgeguarding them.
Which isn't to say you can't win against them, it's within the realm of possibility. But it's such a steep hill to climb and the challenge has nothing to do with what Bowser does to other characters, but how he can get them to let him do it to them.