Well, our defense was really awful last season, and Otamendi is significantly better than any defender we have.The problem is most fans are blinded by the excitement of a new signing and Ed seems sometimes that he acts like a fan or is desperate to appease to them. Otamendi is Di Maria all over as far as I am concerned. He had one great season, does not fit the profile of what we do and how we play and will cost a ridiculous amount. But just because there is the established narrative that our defence is the worst thing that has ever existed, he somehow became the perfect transfer target.
He isn't Hummels on ball playing ability, but he is an improvement on Jones and especially Smalling on that aspect. He hasn't been our first choice (from all reports Hummels was our main target and now is Ramos), but if we don't sign him, then who? Obviously we can go for some young defender like Laporte (who IMO is better than anything we have and has potential to become the best CB in the world) or Stones (who has potential to become one of the best CB in the world) but the last time we went into that direction it didn't end well, and currently we need more an experienced defender (although not a world beater) more than someone who has world class potential, but at the moment wouldn't improve our defense that much.