It’s going to take years. Quite frankly there are only 3 players on this team that would be in the rotation (Top 9) for a NCAA Tournament squad. If any of those three transfer then you have to start completely from nothing. It’s a minimum 2-3 year rebuild at this point.
Here is my dream scenario, and the only reason why you fire him before the season is over. You could hire somebody like Matta or somebody who currently isn't a head coach. There are currently no rules governing contact with recruits if you aren't employed. You get in touch with Matta right now, negotiate his hiring. (Similar to Huggy at KSU). You have Matta recruiting like crazy for this offseason both in the portal and with high school recruits. You hire him ASAP after the season to get kids to sign on the line that is dotted and basically recruit an entirely new team and try to hang on to Hunter.
Otherwise, I agree with you, it's a very tough rebuild and it's going to be really tough on the new coach. McD wasn't a good coach here, that really can't be debated, but taking over a roster with basically nobody on it is tough to overcome unless you're just a crack recruiter.