Yeah ok we know ROB can't fight Marth at close combat and be able to outzone a huge sword there.
That's why he just shoots projectiles at them from afar, or uses side+B to run away and then can rush back in and either dair and grab or fair and mess up Marth's spacing. ROB isn't supposed to outzone Marth with his little arms (if he did, that would be rather sickening, frankly, since he could then outzone almost literally every character with his aerials). But he has lasers and stuff to help him keep Marth out, or he can shoot his gyro to mess up Marth or even shoot it, grab it, and then go up and shield, because he can throw it as a very quick OoS option that will let him setup for more attacks.
If you wanted o only play a zoner, ROB is not the character - he's like the 5th best zoner, not the best.
But the fact that he's like 5th best at everything is a problem, because that means he beats many characters at their own games, or can just fake being the best of that group against anyone who's X game outclasses his.
Marth is not a bad matchup for ROB - he can actually gimp Marth with his projectiles [especially laser] (something that others struggle to do, given Marth's wide sword range that helps protect him coming back) and Marth has to weave through his [potential] projectiles to approach. Then even if he gets close, ROB can move just a little to mess up Marth's spacing and a grab leads to combos, as do certain good hits like dtilt and utilt. Sure ROB's attacks don't hit everywhere at once, but he doesn't need them to, since so many of them hit exactly where they need to so that they link to other aerials.
If Glyph wants to say otherwise, I'd be curious to here what he thinks Marth can do that's so detrimental to ROB, because I haven't seen it.