Yeah, and that attitude there is exactly that of someone who overestimates DK.
And by unsafe on shield, I meant that if DK attacks someone's shield, he is easily punished. All Diddy has to do is shieldcamp with a Banana, wait, and once DK tries to attack, he can glidetoss out of shield and it will punish DK. Very safe, not much DK can do to avoid it. If you try shieldcamping against Diddy, you lose because his Dash Attack cannot be punished out of shield.
The only thing that makes DK "good" is to the extent at which he can punish a mistake. And in high level play where very few mistakes are made, DK doesn't actually have many ways of creating openings. He almost completely relies on people making mistakes because if he approaches, he gets punished out of shield. This is where you guys overrate DK. You guys almost always assume that for whatever dumb reason, someone will get F-smashed eventually, getting them gimped at like 70% or so. Against someone who is camping against DK, he doesn't have any good ways to open up a person into getting F-smashed/DK Punched/etc because they all are very unsafe. As Cyphus says, DK is just a bag of tricks. He doesn't have much in terms of reliability.
DK's MOST safe approach, B-air, has about 20 frames of ending lag in the air (and if you do headbutt mixups, you are vulnerable for over 40 frames). That is way more than enough for anyone to jump out of shield and punish or in other cases Up-smash out of shield.
Also, DK's Up-B is more obvious than Diddy's recovery. It only goes one way. If you don't make it to the ledge before Diddy hits you with a Banana, there is enough hitstun for him to spike you before you can do anything else. And intercepting DK when he's going for the ledge is not hard at all.