Here's my take on ROB:
At low to mid level, ROB is good. Up smashes that scoop you. Nair that seems nonpunishable. Up b for days. Spam.
These are a few things that make an average player want to throw their controller. And that's cute.
At high level and above play, it gets less and less cute.
We are punished for our size, our linear recovery, our lack of combo breakers, our not so safe SH nair.
We are called out on our gyro gimmicks, on our upsmash only hitting at a wide reach while they are on the ground, and our lack of tilt range.
This is where top lvl ROBs usually get further ahead of the pac. Because to compete with ROB at a top lvl requires a lot of discipline. It's knowing how to use your recovery to the fullest, how to do gyro setups on a whim without making them obvious, how to insta toss into combos, how to mix up landings to a science, how to use every movement tool such as instant gyro cancelling and perfect pivots to make every moment worth while.
I honestly see ROB moving up. Especially if I can ever get a true handle on the character. And I would consider myself a high level ROB who sees a ton of improvement for the character. I've yet to see a ceiling in a long time, tho I thought I did in the early days of Wii U. Now my mind is changed and I must lab more, I must practice more, and I must explore more. I must take a very limited number of options in a tight situation and choose the best one.
I perhaps see ROB, at nearly his fullest potential, as a top 10 character. Assuming that what I see left to work on is virtually his fullest potential. ROB got a lot harder to play in this game than compared to Brawl at high level. But the reward for improving will pay off more in this game.
tl;dr
ROB has a ton of untapped potential. And I honestly see him as a top 10 character if we keep moving in the right direction.