In theory:
1. Maguire should be our best defender in a 2 man pairing due to his aerial strength and the weaknesses of his contenders, apart from maybe Tuanzebe, who should probably be thought of as about a 25M (Prem tax) value player based on his season with Villa and his age, assuming he can stay healthy, considering what Mings and other comparables have gone for. So it's not exactly shocking he might be better than Lindelof, who was bought for about 35M and if we could do it all over again we wouldn't buy and would have just kept Blind and not spent the 20M replacing one clever, athletically below average probably #3 or #4 level CB (especially a left-footed one!) with another.
2. Maguire might not be first choice in our best back 3 since Lindelof (smart, weak) is basically a classic middle CB like Conor Coady. Neither has the athleticism to compete out wide against strikers but they're smart and can marshal a back 3 from the middle, which we don't really know if Maguire is up for, and then he's competing with Tuanzebe or Shaw and Shaw's left-footedness and consistency at LCB is pretty high for me, when I think of his games against Salah and yesterday and others. He just seems not to get into trouble there, and his inability to get into the other team's box (like Robertson) or hit crosses from deeper (like TAA), which are his big drawbacks as a fullback, aren't relevant (though you'd still love to have the 2nd).
3. Just as Leipzig ended up pairing two teens in Konate-Upamecano, we might end up with a Mengi-Tuanzebe pairing sooner than people think. Whatever you think of Maguire, we're not talking about taking 2015-2018 De Gea or current Bruno or even Fred here in terms of quality performances. Apart from Van Dijk and Laporte (when healthy), the other big teams constantly rotate their CBs since none of them are consistently as good as their first choice midfielders or forwards. I for one did not expect Rudiger to be 5th choice or whatever at Chelsea, and I don't think Arsenal and Spurs fans or their managers have any idea who their first choice CBs really are (apart from Gabriel but obviously small sample size).