I don't think so, Bowser really has good punishing options, he's mostly held back by the fact that he doesn't have the ability to force approaches in most match-ups and a lot of people can force him to approach (sound like somebody we know?). Actually, there's onlythree characters that make this "amazing punishing, but basically non-existant non-melee game" idea work... Marth, MK, and DK. The other characters that do it are Zelda, Ike, Bowser, Ganondorf. Basically, all the ones that make it work are very powerful in the metagame, the ones that don't are universally low tier, and the difference is whether they can reliably force approaches generally. However, every single one has one thing in common, approaching them in almost every match-up, hurts. You wanna outcamp the ones who don't make it work, not approach them.
But...
So, dtilt is safe on block, he can't punish with fortress (probably the only possible punish). Then this match-up is a lot more managable, unless he's got something longer ranged that's also safe on block. (PS. I just double checked, dtilt IS safe on block).
If he tries dealing with our camping with fire breath, it's got a long cooldown plus it doesn't hit till frame 23. Fullhop-> fair/dair (bair at lower percents), Fullhop-> Down-b, they all punish, I just tested it.
Ok, so basically firebreath won't be doing much, he's forced to approach. Actually, I'm leaning towards a dead even in this match-up, the biggest issue he'll give us is that up-b really messes with combos and if we make a major mistake, he can grab, since he's forced to approach via dtilt, it's not too much of an issue.
Of course, if he didn't have those crazy options (grounded up-b still hurts, even as an approach), this match-up would probably be in Ganon's favor, but what can we do?
50-50, 45-55 at worst?
edit: Yea, complete turn around, a little hard data does wonders.