I think fans need to manage their expectations of Ugarte and how much better he would make our team.
Casemiro has better forward passing, shooting and aerial ability in attack or in the midfield and set piece duels.
Ugarte has clearly got more legs and safer passing. I don't know how useful the safer passing will be when Ten Hag mainly wants the CDM to play forward quickly.
One area where Ugarte can also match Casemiro is with his passes out wide as both are closely matched in that regard.
I would believe that Ugarte isn't a Ten Hag signing as he is nothing like De Jong/Rodri/Neves who are the types of CDMs that a possession based side would ideally have. There's a reason PSG upgraded with Neves after one season of Ugarte and it was because they want more forward ball playing and playmaking from the CDM.
I think we have to hope that Ugartes skillset more suits the Premier League and the upgrade on Casemiro's legs is enough to make us more solid defensively. I don't think it will necessarily make us better as a team looking for more control of the ball, or better in attack. But if it makes us more defensively solid it might be a step in the right direction overall.
I believe this signing is just as much to do with Casemiro's contract and high wages than it is getting a better player than him. Ugarte is going to have to cope with the same challenge that Casemiro has to deal with, of being asked to play forward, and play forward quickly. I'm not so sure he's that good overall.
I'm hoping he can plug the gaps defensively better and use his good long range passing to get the ball to the wide players. I think we'd all settle for that right now, but anyone expecting or wanting a player that can do it all, in terms of tackle, run, assist and score should probably lower their expectations.