At best, he's a bang average Championship striker whose confidence is shot to shit. We should never have signed him, not for £2 million and, it goes without saying, certainly not for £20 million.
His 24 goal season came when Swansea were just relegated from the Premier League, and like most relegated clubs, were tipped to go straight back up and they often dominated games. They had a good midfield and defence, but had sold/loaned out all their forwards (they'd just got rid of Borja Bastón, André Ayew, Jordan Ayew and Wilfried Bony), and so McBurnie got his big chance. After a good start to the season for him personally, over the course of the season, they looked more and more to McBurnie as the central focus of their attacks.
This version of Swansea, with Graham Potter as manager, Rondon, Naughton, Dyer, Routledge, Fer, Daniel James, and so on, and PEAK 24 goals-in-a-season McBurnie could only finish 10th in the Championship. It was a personal triumph for McBurnie ("play in McBurnie", being pretty much the only remaining choice they had!), but pretty shitty output from the club/tactic as a whole.
We signed him on potential. IF he can score 24 goals for Swansea in a season, maybe he can push on and score 20+ in the Premier League? Of course, as we now all know (and the professionals at the club should have really realised this from all his other statistics... )... he's not even close to being Premier League quality. At his absolute best (and the signs are that he's already peaked!) he was a decent mid-table Championship striker.
McBurnie has two problems at this level for us. The first is that his confidence is clearly shot to shit. Football is a confidence game. We had a disastrous season last year, and (rightly or wrongly) McBurnie caught a lot of flack for that. A league goal seems utterly illusive at the moment, and even if he did get a goal, it doesn't feel like he's anywhere close to scoring double figures across as season, let alone 20+ goals again.
The other problem that McBurie has, is that even at the age of 36, Billy Sharp is twice the player that McBurnie is at this level, and if you're going to "throw a ball in the general direction of a striker" in the hope they get something on it that generates a goal, and you had a choice of Billy Sharp or Ollie McBurnie, well.. that's no choice at all, is it?
With the right manager, the right club and the right team mates, he could maybe push on again and perhaps even become a competent Championship striker. But for Sheffield United, McBurnie is a busted flush. It's never going to work for him here. He's a square peg in a round hole, his confidence has gone, and the stench of the £20 million price tag (not his fault of course) clouds everything he does/doesn't do. He needs to move on, for his own good as much as ours.