I don't see Mitchell play up to his forty speed when it comes to pure deep routes. Worthy simply has more quick acceleration than his teammate. On an intermediate crossing route, digs, sure, I could see Mitchell making those big plays and using his size to shield the ball, get more YAC. Worthy averaged less yards because he had more targets and catches (twenty more) than Mitchell, and a lot of them were shorter area bubble screens to get his speed into space. Mitchell had more touchdowns than Worthy and a longer reception, but by less than eight yards.
I'm not saying I don't want Mitchell; I'd be ecstatic if we traded down and got Mitchell. He has vice grips for hands, and even though I have concerns about his compete level, I wouldn't say no to a very talented young receiver. But I prefer Worthy for his easy speed, acceleration, and route running. I feel that he's a better deep threat, a better route runner, and a Desean Jackson clone, only without the maturity issues that Desean had.
Desean Jackson is what I see. (You mentioned Jaylen Waddle, and I see that, and I'll also say DeVonta Smith, who is literally 170 lbs., so I don't automatically see size as a problem.). Had he not had the maturity issues, Jackson could've been a solid receiver for McVay's system. Brandin Cooks and OBJ can hardly be considered bigger receivers as well.
And considering that Texas has had a solid running game running basically 11, and for the past two years, they've had one of the best draft-eligible running backs in college (Bijan Robinson, Jonathon Brooks) as well as a bunch of solid complimentary NFL-caliber backs (Roschon Johnson, Keilan Robinson), I don't have issues with Worthy's blocking on the perimeter. He's not going to be Kupp or Nacua, but he doesn't have to be to be an impact player.