I rate him much higher than you do. He walks into our team, for me. I’d take him over Bruno any day and being as he can play left as well, we could play them both most of the time. If there’s one team who really needs his guile and quality it’s us.
I can see the argument of them being on a similar level at best, being different types of #10's, though Grealish only showed half a season of that form and without the same level of production while Bruno showed it for far longer. Grealish is a top player for sure, but IMO Bruno is in the tier below just De Bruyne (and not far below, but admittedly below) on par with any other attacking midfielder around. Grealish is more of a dribbling type of creator while his range of passes isn't as good as Bruno's (who doesn't create much through dribbling), while Bruno provides loads of goalscoring input and shot taking input which Grealish doesn't. De Bruyne kind of is a mix of them as he provides very effective dribbling but also provides a good amount of shots while keeping a very high level of passing.
A big plus for me is fitness though, as Bruno just doesn't get injured, yet that gets overlooked all the time.
Anyway, if we didn't have Rashford or Sancho, then by all means get Grealish. But we have them both now, Sancho was priority for me as he can play on the right and is 5 years younger, so he works with whatever combination we want. Grealish basically competes directly with Rashford and Bruno and ignores are biggest hole in attack which was the RW, so thats why I was all out on him. Even if you think he's ahead of Bruno or Rashford (again, which I disagree with for our team needs), it's at best a marginal difference, not a 100m difference at the expense of other positions. I like having an inside forward on one wing and a creator on the other. We have that with Sancho and Rashford now, or Sancho and Greenwood, so in my mind we're set on the wings and #10 even if Pogba goes. Rashford is our long term LW for me, and we have depth past him, so Grealish was just unnecessary for me.