He is a very good defender, but these Nesta/Maldini comparisons need to stop. It's like comparing Bellingham to Zidane - nonsense.
There are three main reasons why losing out on him will hurt us though:
1.) It seems he really wanted to join us and would have remained loyal to the cause - having an Italian CB as a foundation piece/cornerstone of the defense has always been part of our identity/DNA
2.) He was relatively affordable in terms of both transfer fees and wages, and finding someone like him again might be far more costly
3.) We might end up losing Bremer next summer, and then we'll need two new CBs because the others are either absolute garbage (Gatti) or too raw (Huijsen)