Doncic and Porzingis should be a good pair when you consider some of the other top pairs per the +/- comparison. They clearly did not play as a top pair last season. I think it is due to shortcomings in both players. Doncic is still young and Porzingis has been hurt a lot. That pair should be able to do more than they have done. For example, they should be able to be as good as Collins + Young or Randle + Barrett (I see I had a typo in my original posts on the NYK pair).
As to Porzingis specifically, he is certainly not going to be the big part of a top pair like Gobert, Giannis, Jokic, Embiid,... but I think he is still a good player. As someone said, maybe more of a good third to add to Tatum and Brown.