Did you want the Kings to trade Fox for Porzingis at the time? That's not a trade that 90% of Kings fans would have made at the time so I'm not really a big fan of revisionist history when it comes to things like that.
Despite all the dysfunction in the front office and personnel mistakes, Fox is performing well on the whole this season and showing that he's becoming a better player at only 22 years old. There's still much reason to believe that if he's surrounded by good talent that actually isn't on the IR every other week, he can be a major foundational piece.
Porzinigis is a good player, but is a couple years older with a concerning injury history. No chance I'd make that trade then or now.
Kind of like wanting to draft Mitchell with the 10th pick. Only Blob and a couple other posters on this site can really say that because they were calling for him before the draft. The rest of us didn't want to draft a combo guard who was semi redundant to what we thought would be our two best players in Fox and Hield. I certainly wish Vlade would have drafted Mitchell but I can't really complain about it since I wouldn't have drafted him myself at the time.
As I've said many times, much of player success has to do with situation and fit. As far as we know, Mitchell wouldn't be winning in SAC right now either. Because of all the draft and FA misses and other happenings. He wouldn't be playing in Utah's system with Rudy Gobert and others.
You swap Fox or Buddy with Mitchell and their stories become drastically different. Mitchell would be losing here, Fox or Buddy would be winning there, even if not at the exact same level. Because the franchises are currently in and have been in different places.
And I recognize that the above doesn't apply to all players. Every player and situation is unique. But unlike a player like, say, Devin Booker, Fox and Buddy have been players than can kinda fit in anywhere. Because they don't dominate the ball or jack up 25 shots every game.
Mitchell would be piling up nice stats here in SAC but would be suffering the same team fate as DeMarcus Cousins and now Swipa.
Now Swipa and Mitchell together? Perhaps that'd be a bit different. Who knows.
And if those two were both drafted w/o trading Cousins (which was still possible because you never know how the lottery would have went) then the KINGS might have really had something.