How is it a blind argument?
You are the one comparing the talent of the two rosters.
It's a given Sparano had more talent on his roster, but that's why you adjust the results. Was the talent on his roster really worth 11 wins? The expectations for that squad was somewhere between 4 and 6 wins. That's a +5 to +7 differential.
Here are some samplings on expectations at the time:
http://www.espn.com/nfl/preview08/team?team=mia (prediction: last place in AFCE)
https://www.si.com/more-sports/2008/08/29/predictions (Don Banks 2008 prediction: 5-11)
https://walterfootball.com/offseason2008playoffs.php (prediction: 2-14)
bleacherreport.com/articles/53121-nfl-2008-preview-and-playoff-predictions (prediction: last place in AFCE)
The expectations for Flores' talent purged roster was anywhere from 0 to 3 wins. That's a +2 to +5 differential.
You have to account for competent QB play being mostly responsible for a win or two, as was the case for Sparano and Flores. Eventually, the team will regress to the mean.
I really can't understand how people can look at the two and make the claim that Flores did a better job. One thing that no one is factoring in is the pressure that builds when a team is pursuing a playoff berth. Sparano's teams kept winning under that pressure. Flores' teams never even had to deal with that kind of pressure because they were out of the race almost from the beginning, especially by the time they actually started winning games.
EDIT:
Funny thing is just looking back at some projections from the beginning of the season, some places like ESPN even projected them with around 5 wins:
While the Dolphins sort out one of the league's only QB battles, all eyes will be on whether Josh Rosen can be the team's leader for the future.
www.espn.com