It's also probably why he got Checkmate in the first place. Not only does Robin have to grab with that bad range, but he also has to be nearly frame perfect to catch them with Uair afterward. He does it too fast, he gets JC Usmash. He does it too slow, he misses due to airdodge. He gets it perfectly, he gets his KO at 90. There's hardly any room for leeway, so getting it on the dot is heavily rewarded.
Just saying, all you have to do is do a quick claw or use a trigger to jump or just be fast w/ your jump button and the C Stick. You can make this way easier for yourself by using the C Stick (set to attack) for up air. There's no point in forcing yourself to have the right timing with the A button unless you just want to for some reason.
a nerf on Sheik's vanish i-frames is prolly the single most common sense nerf that would help. It's not even so much that you will be able to challenge it that much more, but you can force her to recover below the ledge and this makes Sheik's recovery a lot more punishable because you can consistently go for 2 frame punishes instead of being shut out by the above the ledge vanish recovery, forcing Sheik to mix up her recovery more and thus become somewhat exploitable in the process. If she has to recover below the ledge that means ZSS can dsmash -> down b, Sonic gets the free down-angled fsmash, Pika can get the thunder spike...really a lot of characters have good 2 frame punishes so I think this would help a lot. Being able to hit Sheik out of her recovery's start-up more frequently means you can actually challenge her recovery.
Nerfing her 50/50 is really overt imo, she can't kill without it and it's really one of the most overrated things about the char. If you air dodge at 90 and Sheik vanish kills you, that's really your fault. Realistically a vanish at that percent is greedy because up air will never kill you and Sheik won't want to go for it because she doesn't want a stale up air. There's a percentage range where it works and both up air and vanish will kill, but not even every character falls victim to that. People think Sheik can just grab you again and go for the 50/50 over and over if she misses it, but in actuality if she's staling down throw then the lowered hitstun allows you to jump out much more easily, especially as percents climb. The 50/50 is a good source of kill confirms, but it has limitations and workarounds especially with DI and different mixups you can use on the receiving end. Smart players already employ these tactics and make it a bit harder for Sheik. There's too many factors going into play as others have said.
I really just hope people don't continue to perpetuate the myth that Sheik is unbeatable and completely oppressive to everyone. The reason she's the best is that she doesn't lose any matchups, but I don't really see this as a problem so long as she isn't a completely dominant and oppressive. Sure, there are characters that would benefit if Sheik was nerfed. But these types of characters almost invariably lose to other top tiers as well, ZSS, Rosa, and Mario being the biggest offenders as gatekeepers (idt Mario is top 5 but he has more gatekeeper mus than Pika or Ryu). All top tiers lose 55-45 or go even (which are fine matchups) and there's more than enough characters overall that can contend in the MU vs Sheik. Realistically the list of characters that Sheik 'destroys' is smaller than people would like to think and proven this way in practice.