It's not acceptable to concede six at home, agreed.
But, any manager that comes in will at best effect only marginal improvements. Because ultimately, we will not get better players. We will get the same category of players the club has (mostly) looked for, largely without exception, for 24 years - young players with high resale value, or players who are cheap in terms of wages.
Both come with limitations, and those are exposed in times of crisis. This will happen to every coach we pick, even if some get marginally better results by shutting up shop, being pragmatic, etc.
Long term, there is no hope for improvement without running a certain gentleman in the directors' box, and his tax-exile boss, out of the club. So, why go through the rigmarole of another coaching change, another two years of transition, another set of tactics that ultimately will not work?