I don't think the way we played last season is sustainable, regardless of personnel. Sure Ugarte can help break up some of the counter-attacks but he won't be able to stop us from conceding 20+ shots on goal on his own.
I can't pretend to know how we'll try to play next season, and to be honest I'm not sure pre season will tell us much either because of how many players will still be on holiday. However, let's give it a go!
One of the biggest issues last season was we pressed high to try and create turnovers which our quick attackers could exploit (which made sense) but also played with a fairly low defensive line. This left a huge amount of space between defence and midfield which our midfielders had to try and cover. Thus, teams just ran through us and we resorted to box defending. This by it's nature led to a high number of shots being conceded. EtH said most of those were 'low risk' chances, and in fairness he wasn't incorrect about that, but it was still horrible to watch and incredibly risky, at best.
I imagine next season we'll try to also play with a high line, as having quicker/aggressive defenders like Martinez, Shaw, and now Yoro, allows that. In this sense, I can see how Ugarte can work. He'd quickly try and recover the ball, and if he's unsuccessful the defensive line shouldn't be far behind him to close off any space. Ugarte isn't as physically dominant as McT but he's better technically and can play a possession game, even though he mostly keeps it safe and leaves the chance creation to others. That's not a bad trait at all, and along with Mainoo would help us maintain control of matches when we want to slow the tempo, which we often struggled to do last season. He'd also help with buildup from the back, as whilst not being super press resistant, like most south american players he's pretty comfortable on the ball.
There's a lots of ifs and buts, and I think a couple of injuries and you're back to square pegs in round holes for these tactics. AWB instead of Dalot at RB, no Martinez or Shaw, greatly hinders deep build up and leads to Onana going more direct. So we need not just better, but more appropriate depth.
I actually think Zirkzee has been signed with this in mind. He's big and strong, and whilst not aerially dominant he has a great touch and turn. Whether dropping deep to pick up from midfield or taking a long ball from Onana out of the air, he can quickly turn defence into attack, especially with the likes of Rashford or Garnacho on the wings.