I suppose the question I would like to ask is: who thinks that we could have got a real striker and a real CB backup, if we tried harder / were more organized / splashed the cash, as opposed to who believes Ernie et al. that they tried their best and came up empty? Because if you believe the latter, there's not much point whining about it now. Eg, the idea that we "let Boxall go" rather than "Boxall got an offer that we couldn't top without the aid of a friendly genie".
It depends on what you consider a "real CB backup" to be... considering that prior to signing the Fantastic Mr Fox we had 2 CBs in our squad. Even if we couldn't get a proven A League performer or somewhat-experienced professional, why didn't we sign a young CB earlier? After all, neither of our 2 regulars have more than a few seasons left in them so even if he didn't get much time this year he'd get chances over the next couple. And unlike previous periods when we had young CBs on the books (I'm thinking Musa and Adams) we actually have a proper reserve side for them to play in now if they aren't getting first team football. Having a young CB who was in the squad for most of the offseason would have given the ma chance to get used to playing with Siggy or Dura too so they could be more comfortable if they had to do it in a game that mattered. If we then got a more experienced CB as well to be third choice the young guy wouldn't exactly be on a lot of coin anyway - he'd just be at the expense of say, Danoskos (who seems to be our 3rd choice leftback).
Clubs sometimes make bad decisions in the transfer market (Andy Carroll to Liverpool, Falcao to Man Utd/Chelsea, Arsenal Wenger not signing a proven goalscorer or a DM, and so on). I think our decision to not have CB cover signed early enough to get settled into the squad and playing preseason friendlies was a bad decision.