To be clear the vast majority of the "Biden did this wrong" stuff isn't because the posters feel that the US should have kept troops in there longer, everyone agrees we/they needed to get out.
The problem is with the way this "agreed by both sides of the House" withdrawal has occurred, and that lays squarely with whoever is currently in charge, both politically and militarily and that is currently Biden. In his defence I absolutely believe he was sold a lie by his various intel services who I think, for some unknown reason, didn't pass on the accurate reports from troops/people on the ground telling them everything is about to go pear-shaped, leading Biden to say things which, with 20/20 hindsight, now look really stupid. However the response of his administration to Kabul specifically (when "the truth" about the collapse became known) and his actions afterwards towards the press trying to ask him questions have been pretty poor.