I'm not sure there is too much 'fault' to go round here, necessarily.
We know that we only get our hands on the better young players on the basis they will be sold upwards if they do well. Nobody at Palace is responsible for the state of football, they just have to play along. We were always going to come to an end of the positive cycle, and it was always going to be hard to repeat that level of luck/success with new signings. There is no failure in Palace not being able to keep the FA Cup team together, or replace them like for like.
The signings of Johnson and Larsen have been catastrophes, but to be fair, not many of us were moaning about Johnson or his price when we got him, and a good many of us wanted the club to reinvest the profits from big sales into established senior players rather than young hopefuls. To pay the market rate. To not be tight. To support Glasner in his attempts to win in Europe. That's what they tried to do. It failed, but it wasn't mental.
We don't know why La Croix and Munoz were sold, but we do know that UEFA FFP is very tight, that we qualified for Europe again (which was not to be presumed at the point of earlier financial planning) and that someone like Parish isn't going to weaken the team through choice or carelessness. There will be a reason for those sales. Whether another approach could have been taken instead or not, again, it wasn't mental.
In terms of replacements, I was one of those summer moaners complaining that the squad looked deeper but the team looked weaker. That seems to have been proven true (to date, at least). Still, it seems essential for Palace to buy young hopefuls like Gozo, Osario, Khalili and so on (none of whom obviously strengthen the team here and now) if we hope to have any transfer budget in coming windows. We can't stop the process of buying young hopefuls just because the last batch flopped. If anything, it makes it more essential. Personally, I would have focused that money on a couple more senior pros with less sell-on value, but I do understand why Palace do it the way they do.
We didn’t get good enough established senior players in the summer, especially at the back, but we don’t know who was actually available, whether they would actually join us, or whether we could afford them. It is possible that it all makes perfect sense if you know the details, which we don’t.
Finally, I doubt Sage was appointed just because he plays a 343. Let's not forget, he was coach of the year in France and took Lens to second place. Personally, I don't think you needed a crystal ball to question whether, given his lack of experience and apparent tactical approach, he was the right man for us at the time, but we had just won three trophies in a year and were going into the Europa League for the first time. I could understand it if Parish wanted a positive appointment to keep momentum going. At the time, we would all have cried and wailed if he'd gone with a safe pair of hands instead.
They say the road to hell is paved with good intentions. I think, at least, the road to being in a pickle is often paved with decisions that only seem wrong in hindsight, but were reasonable enough at the time. None of that matters now. What matters is whether the current arrangement is likely to work given reasonable time and support and, if not, how most effectively and efficiently to change it.
We all know that only means one thing, and it's not about whether it’s fair on Sage.