Quality mid-20s CBs don't grow on trees, though. Especially not proven and definitely not cheap. Re-signing Collin at what looked like a discount at the time was a no-brainer. It obviously didn't pan out as hoped (ditto for Baah) but you can't criticize the thought process there. Not without the benefit of hindsight anyway. Just like now we know a 33yo Parkhurst had a much better 2017 than a 31yo Collin. We could use some time machine action during every offseason for sure.
Could/should they have signed more CBs in case 2 penciled-in starters were injured all year and DP aged 5 years in 5 months? Yeah, sure, obviously. They did get Escobar, a promising young CB who is an international at 22yo. But then maybe we don't get Royer or don't give Robles/BWP/Felipe raises. Not giving FO/Marsch a pass, but it isn't as easy as "get more better CBs, duh".
I know Parkhurst had a poor 2016, but his ability to organize and distribute would have been a natural complimentary piece to this team. I don't know. I just never felt comfortable with our CB pool going into 2017. DP looked like shit last year and has been generally poor this year. Baah was coming off a very tough injury. Colin had to fight through a lot of stuff to get on the field. To me it was a big red flag and we've been generally below average on the backline all year.