Is it considered a religious error to delay workers in the mosque for a few minutes after prayer for the purpose of reciting Athkar (remembrance) and Du'a (supplication), and what is the ruling on that?

We advise you not to burden people. If the custom is to close the mosque after people leave, then leave with the last of those departing, and complete your remembrance (dhikr) and supplication (du'a) in your home or on the way. You will have a full reward. We advised you of this so that those in charge of the mosque are not inconvenienced by you, or so that no estrangement occurs between you. Gaining their affection and fostering their love is better than staying this short period in the mosque. If it is possible for you to close the mosque after finishing your dhikr, and the person in charge of the mosque agrees to that, then this combines both benefits.