Synergy Sports is a good resource for scouting players, especially because they have video (more if you are actually signed up) so you are able to see exactly how they plays are happening, and the context of the plays.
One thing that people don't look at which is actually very useful is the team numbers, which you don't have to adjust for things like, for example, a spot up shot is counted as being made against you, but you were just hustling and actually helping on a teammates man but couldn't get there quickly enough. You didn't play bad defense there, you actually played good defense, but the shot is charted as being made against you. Now, large sample sizes do correct a big for things like that, but for some players or in certain team settings, it doesn't fully account for that, so that has to be taken into consideration.
PPP = Points per play
Rank = league rank, so top 7 would be good, of course top 3 would be great
11.8% of plays / 0.86 PPP / 34.1% FG / 32.9% 3PT / Rank 1st
Pick and Roll Ball Handler:
19.3% of plays / 0.73 PPP / 39.2% FG / 33.1% 3PT / Rank 2nd
2.5% of plays / 0.77 PPP / 37.6% FG / 27.4% 3PT / Rank 3rd
9.7% of plays / 0.82 PPP / 41.6% FG / Rank 6th
6.4% of plays / 1.03 PPP / 50.3% FG / 41.7% 3PT / Rank 8th
11.8% of plays / 1.1 PPP / 53.8% FG / 37.4% 3PT / Rank 8th
There's the obvious things. Even if you can defend the play following an offensive rebound or defend well in transition, those are some of the most efficient plays in the league, so you want to limit those opportunities as much as possible.
The areas that jump out would be:
1) Defending the spot-up shooting, Doc really did his work in regards to this one, and that is just excellent
2) Defending the ball handler on the pick and roll, props to the perimeter guys and the big men assisting them on that one
Pick and Roll, Roll Man (this includes pick and pop):
5.9% of plays / 1.14 PPP / 58.5% FG / 47.1% 3PT / Rank 29th
4.1% of plays / 0.98 PPP / 44.1% FG / 40.1% 3PT / Rank 25th
9.7% of plays / 1.23 PPP / 63.8% 3PT / Rank 18th
9% of plays / 0.84 PPP / 36.3% FG / 32.7% 3PT / Rank 16th
Cut's like offensive rebounds and transition are areas you don't want to give up scoring in. Clippers gave up 16.1% of scoring plays on cuts and offensive rebounds combined. Isolation is not really a weakness, that's just mediocre which is perfectly fine. SA for example was 24th in PPP given up in isolation, but they defend well as a team. Isolation in general is inherently an inefficient play in comparison to other plays, so if you can defend everything else well except for isolation, then you are fine.
The areas that jump out at us obviously would be:
1) Pick and Roll / Pop where the team is 2nd worst and gives up a miserable 47% 3PT
2) Defending players who are making cuts
Why is the defense against the roll man so poor? We all have our theories. If you have a membership and have time, there's 649 plays of defending the roll/pop man on the pick and roll that you can watch. Cut's are actually also a big deal, 9% of opposing offenses is a lot, so again, why so poor at defending cuts? Again, we have our theories, but there are 1007 plays of cutting to watch if you would like. Defensive awareness / getting lost could be a factor, not enough length when the team is helping against a cutter (ever see the comedy when J.J. comes and helps against an interior play and it's like he isn't even there?), but some of the plays that count as "cuts" are essentially drive and dump offs to a big man near the baseline, so here the ability to contain penetration or how to not over-help vs penetration comes into play.
Now the defense off screens also isn't good, but probably a bit less crucial than the other two areas based on what teams run most frequently.