De Ligt in "that" Ajax season was far better than Martinez at Ajax. He was so good even I rooted for him. As for not being player of the season. Bit hard if it's between you, Frenkie, Tadic and Ziyech who all had their career best season.Not really true. They are also completely different players but wouldnt say de Ligt at Ajax was better than Martinez in EtH last season at Ajax. Martinez was Ajax' player of the year, which de Ligt has never managed to. Not sure where your hard claims are coming from.
Martinez was also formidable in his first season at United, de Ligt was also great that season at Bayern. Not much in-between them. Last season is hard to tell, Martinez barely fit but finished the season strongly with a great display in the FA CUP win, part of a wonder duo at the Copa also with victory. De Ligt finished the season strongly at Bayern too.
I feel Martinez has the benefit of being a perpetually injured player at a struggling side which makes him a target of the if only he wasnt injured sentiment. Not saying he's bad, but I read shouts that he is in the 5 world best cb's and that's just crap.