I have yet to see a player that wasn't a good defender in his first few years in the league end up as a defensive anchor. They can improve to not being a liability, sure, but a defensive anchor is another thing altogether. Gasol was DPOY. I bet you that Cousins will never ever even make NBA 1st team defense, very likely not even 2nd team. That just isn't his calling.
We dont need this scary, athletic shotblocker like Ibaka f.e. If we arent able to get a defensive anchor via trades and FA, we need to develop DMC. We literally have no choice. Everything in basketball outside of the physical gifts is coachable.