I read a news report where it was rumored that Chelsea will table a bid for Maguire well if it real I think that will be a better alternative for him (Maguire) to leave instead of sitting on the bench at Man Utd after stripping him the captainship band and this could affect his international career having been one of the favorite player of Southgate Moreso the duo of Varane and Martinez had a solid partnership at the central defence of Man Utd last season consequently subjected Maguire to the bench hopefully they will retain their position this season, Evans a former club defender had also been signed by Erik ten Hag on a short term loan deal thus will definitely be another competitor to Maguire thus he will have a limited playing time.
I doubt if Chelsea really want to sign Maguire. There is nothing special about this player, he is just a controversial defender. I'm sure it is a rumor only, Chelsea will never try to negotiate with Man United to sign Maguire. Anyway, I agree that Maguire is better to leave Man United because he is probably difficult to get a chance playing regularly there. Not sure which team is serious to sign him, but he should leave if there is an offer from other teams. His career won't be better if he stays in Man United, he can't compete with Varane and Martinez.
I am not sure if Chelsea is still interested in Harry Maguire for now...before Pochettino became the coach of Chelsea fc,I read and was sure Chelsea was interested in Maguire. But since Pochettino came and even had to sell players that are better than Maguire, I really doubt he will be needing the services of Harry Maguire.
Talking a out the usefulness of Maguire, I am confident the English defender will be useful to many clubs. He is just finding it difficult to adapt to Erik style.