There is no excuse for the Suns being this bad on defense, even though they are soft in the middle. IMO, it's not only a personnel issue but a coaching issue as well.
On this I agree 100%. Look at someone like Alex Caruso, who is undersized as a SG/SF and isn't exactly in the top half of the league in terms of athletic ability in regards to speed, strength, vertical, etc yet he's an All Defensive level defender. Some of that is coaching he's received but it's also personal sort of drive to be that. That's lacking from our players with the exception of Okogie, Dunn, and maybe Oso and Royce. Their motors don't quit. A lot of the rest of team suffers from too manys peaks and valleys in terms of their own commitment to defense. Beal seems the most focused of our Mid 3 on defense but I think that's in large part because he handles the least of an offensive load so he's compensating on D. Coaching could improve our defense some in terms of scheme, like how we played better D last year, but the effort is still lacking with the personnel who make up this team. So it's almost destined to fail or be mediocre regardless of coaching because that was the ceiling of our D last year with a better scheme. As long as this teams in place then good D won't be on display.