We don't have any long term solutions at CB outside of Sakho at this point. Having young depth isn't a luxury in the modern game, it's a requisite. If you really think that more than 1 of Kolo/Skrtel/Agger are going to be squad fixtures past next season, then it's a valid point, but I can't see it playing out like that. Sakho is a squad fixture, but Agger/Skrtel/Kolo are all fairly average, and we don't have much of anybody in the pipeline given Coates tearing his ACL.
Hindsight is 20/20 and all that, sure now we could be using an extra DM, regardless of if they were a fairly average player given our options, but it's absurd to track all the way back to the summer window. I imagine having an extra 8M now wouldn't make a difference in if we sign someone or not, 15M even. I'm sure there's a 15-20M pool available if we pull the strings we need to, it's just a matter of actually finding the right target, agreeing on him, negotiating a deal, and completing a signing that we keep getting hung up on.
Surely we can't simultaneously be broke and be scouting Salah for several months. The front office would know the FFP situation well before the window and wouldn't even bother with the intensive scouting and talks given we had no funds anyways, unless we planned on moving some players, which clearly hasn't been the case. There hasn't been a single decent rumor indicating we're looking to sell anybody in several months, which is telling as well.
All this tells me that we have money to spend, but can't find the right target to spend it on. Whether or not that hurts us in the long run remains to be seen, but for the time being it's not looking fantastic.