How were you able to make drops or pick ups in January if it’s a keeper league?
So I am going to go against the norm on this one. In my opinion since this is not a dynasty league, all rosters should have been locked as soon as the 2020 season was over. The 2021 season begins once players decided who their keepers are and locked in. Once that happens then draft pick and keeper trading can begin. THEN once the draft happens, you can once again use the waiver wire. I do not see a point in that timeline when someone should’ve been able to drop or pick up Mixon. Unless previous stated in the Rules that pickups were allowed in the off season and those players are able to be kept as a last round pick, then not only should Mixon be off your roster but unfortunately go back to his orginal owner.
This is just my opinion and this would be a totally different story if it was a dynasty league.
Good Luck with everything