Well that's not disrespectful either. That's an opinion on my part based on my decades of experience watching United and other top teams.
He's OK, he's solid, but he's not the level of an elite full back.
I could name some elite fullbacks as examples, but the problem when you do that on here is that the point becomes lost as it descends into a lowest common denominator argument about whether "Player X is better than Player Y"
BUT...if I were to say, for example, "Ashley Cole"...99.99% of this forum would agree he's an elite fullback and much better than Dalot. So there's the level we should be aspiring too, and that's the level I sat and watched at United, and from our best opponents from the PL and around Europe for two decades. Dalot isn't in that bracket, he's in the 'Spurs' bracket.