All advanced defensive metrics are imperfect and rather flawed. Defense is best measured by watching film (or the games), having an understanding of a teams defensive scheme, who the other defenders are on the floor, opposing offensive players, in-game context, and numerous other things that can't really be measured on a stat sheet. Also no one number really is going to tell a story here. In the shortest, simplest term, this is the "eye test".
For those unable to do the work above, you pretty much rely on experts on this case who do. In the NBA, that's pretty much the media, which as we all know can also be imperfect.
Advanced defensive metrics in general favor bigs. If we were to take Defensive Win Shares (DWS) serious, is anyone going to agree on this forum that Vuc is the 6th best defensive player in the NBA? No, I don't think so.
Are there good defensive players in the top 10 of DWS? Yes. Now if I have some knowledge of who are good defenders in the league prior to reviewing these stats could I draw some conclusions from it? Yeah probably, but I can also point out to you the flaws.
If you look at the All-NBA Defensive Teams from last year, those players ranked 3rd, 5th, 8th, 10th, 11th, 12th, 13th, 41st, 57th, and 70th in DWS. Jrue Holiday is that 70th player, and also a guard, which these stats mostly punish. (Please note that numerous players are tied in DWS, so these ranks can change suddenly with a refresh on basketball-reference).
Though oddly Luka Doncic, a point guard and a player not exactly known for defense, ranked 6th in DWS last year. His teammate, Dorian Finney-Smith, who got some votes for the All-NBA Defensive Team, ranked 22nd.
When looking at the Bulls this year at DWS, Vuc, as I previously stated is ranked 6th (well, tied for 5th actually with Brook Lopez at 3.8). DeMar, Zach, and PWill all are at a 2.0 DWS and tied with several other NBA players at what I guess would be 34th in the NBA. Does anyone really think DeMar and Zach are great defenders?
Caruso, largely considered the Bulls best defender, is at a 1.9 DWS.
I think I saw block % mentioned as a defensive metric, but that stat doesn't do anything but measure blocks. Ability to block is a part of playing good defensive, but just being good at blocks doesn't make you a good defender.