No question Lovie should have been given the slip during the 2018 season. That was the game where I gave up completely on the Lovie regime, though it should have been after the Penn State game that year. The biggest blunder of Whitman's tenure was maintaining Lovie after that season. Season 3 should show progress; it clearly did not, and the defense was historically bad. Unfortunately, Lovie was retained and had a mirage bowl season in 2019, which meant he parlayed that "success" into another lost season in 2020.
However, I cannot buy into the hypothetical game you suggest for all the points I made prior. I also think the recruiting impacts of a proposed lame-duck Cubit 2016 season would have made it overly challenging for a new coach to get any positive traction (in today's landscape it would be easier given the way the portal works now). That is why I despise these hindsight analyses. Every recruit knew the Lovie name, so it partially helped through 2016 season. We may have been behind two seasons of recruiting had Cubit been retained. The Lovie hire was certainly a major risk, but one that I believe Whitman had to make given the contract situation of Cubit he inherited from the administration.
The Lovie hire failed on the field as a fact, but the program foundations were piggybacked off the hire. The mistake was sticking with Lovie through 2020 season (should have cut losses after 2018 season), not hiring him in the first place.