At some point, we need to appoint someone to undertake a mass clean out of the squad and completely rebuild. Other than Bergvall, Gray, Xavi, VdV, Kudus, and maybe Tel, everyone needs to go. That isn't going to be accomplished in one or two transfer windows.
Yet it'll never happen if we keep sacking managers because they don't immediately have us challenging for Europe. While we keep appointing a new manager every year, the deadwood stays, and the squad becomes even more frankenstein with nothing but club purchases. That will eventually lead us to relegation with how competitive the league has become.
Say Frank is sacked tomorrow and we appoint a """longterm""" replacement like Xavi or Terzic. Maybe they get us playing better, maybe they don't. But if they dont - which is highly likely given the terrible state of the squad - the same people calling for Frank to be sacked will be calling for Xavi/Terzic to be sacked in October. Then the cycle just repeats itself.