De Ligt can be part of a great defense in my opinion, one that can even rival Arsenal's current backline.
He just needs someone next to him who has pace, can deal with any player 1v1, and can eat up ground quickly. Martínez is not good at any of these things, and de Ligt wasn't made for this either. Yoro is, however, and the only thing that could make him a better partner for de Ligt than he already is in theory, is being left-footed. But he's just 18, and I expect him to be quite raw in his first 1-2 seasons.
My issue is that Maguire is already capable of doing 99% of the stuff that de Ligt does. So why not sign a wide defender like Branthwaite and put him next to Maguire, to create a much more balanced CB duo that can deal with almost any type of defensive threat, rather than opt with Martínez next to de Ligt, a duo that doesn't have enough pace, and often not enough height either.
We basically already had the de Ligt profile in the squad, with no signs of physical decline IMO, whereas we ignored the missing wide defender profile...or you could argue that we decided to heavily depend on the 18 year old kid from France as our wide defender.
At this point, Lindelöf should replace Martínez who should be pushed to LB or the bench, with Dalot/Mazraoui at LB. And then we'll be a bit better despite Lindelöf also being far from the ideal wide defender. But Lindelöf-De Ligt would be a much more balanced duo and they'd be much more comfortable next to each other than De Ligt next to with Martínez.