It's not a piss take no, since SAF left United have won a Europa League, EFL cup and FA Cup.
Chelsea have won an EFL cup, two premier leagues, the champions league and the club world cup.
I'm pretty sure Chelsea have had a higher points per game and had much better recruitment over that period too. The major issue for United has been the changes and stagnation where-as under Roman Abramovich he made good calls frankly.
Being purely objective Chelsea have had a better decade, 2 premier leagues AND a champions league, United haven't come close honestly.
The closest United came is under Jose with finishing 2nd in the league and winning the Europa League and EFL.