DL said at the start of this season that he would judge Corbin on how well the team does defensively, and not on the W/L column. Any team can be taught to play solid defense. I'm not saying we could have been top 5 in defense, but maybe top 13 (where the Suns, who have less talent, ended up in defense). Dead last is inexcusable.
Just because someone can be taught how to play defense does not mean they will have the ability to do so. Again, Clifford is doing next to nothing on defense and his team was ranked 5th. Talent is everything in this game.
Your insistence that the Suns have less talent than the Jazz is hardly true. They have two players who are better than the best Jazz player, and both can impose their will onto opponents in the set and open court. The offensive threats they pose automatically make their defense better as the opponent has to respect their ability to run and gun, and responds by running more conservative offensive schemes. Also, when opponents have to respect your transition ability they cannot send as many offensive rebounders, and have to get back on defense instead. This had a significant impact on the Suns points allowed per 100 possessions (offensive rebounds continue the same possession).
The Jazz don't have these luxuries -- they'll improve on defense simply by getting a guy who can lead the charge and a rebounder who can outlet pass.