ROB can't really hit you at long range in neutral, and his projectiles by themselves don't set up anything easily, so he has to play conventional footsies to get anywhere, where he's honestly not very strong. His tilts have okay range and speed, but don't do much damage. And you have to keep in mind ROB is tall and has one of the worst shields in the game. The nerfs to ROB's footsies make this weakness very apparent.
Saying ROB's KO power is reasonable is like saying Mario is amazing at KOing because he can kill people at like 80-90% with F-smash. Now, ROB's buffed U-throw does help him significantly, I will give him that, but you have to remember his damage per hit is about as low as Mario's, and he doesn't have the same followup potential either.
ROB like Mario is easily juggled and edgeguarded. He's harder to gimp and heavier, which helps and makes him slightly better overall, but if you're negative state is one that counts on tanking hits you can't avoid, you probably should be a hard hitting character or highly dominant in neutral. Unfortunately, ROB is not Rosalina, nor is he Ganondorf. By the way before you argue Ganon's viability again, I definitely believe
Ganondorf beats ROB convincingly, who outranges him and can easily take advantage of ROB's huge frame, and because ROB is very bad at edgeguarding low recoveries, and then because ROB's hits just do very little damage.
The primary upside to ROB is lasers have the potential to allow ROB to maintain momentum at long ranges due to their juggle potential, and when ROB is able to win neutral, the Gyro gives him more control options. But this doesn't make him very good at dealing lots of damage very quickly on a read, nor does it give him really good ways of finishing people early.
I believe ROB is a character who overall doesn't get KOs super easily, suffers a lot due to his size, shield, physics, and negative state, and his nerfed neutral doesn't protect ROB nearly well enough to make him very strong.