I don't think so. Is there a reason why you don't want users creating polls?
On a wiki, people flooded the discussions with the polls (especially image polls). They are attractive somehow due to which they get more than 50 votes while the people who do the actual discussions like post some questions and answers, tricky questions, or share opinions get less attention, only 4-5 people reply on it. Due to which I wanna stop/ban the polls on discussions. Admins had the right to enable and disable polls on discussions before, they were able to do it by their wiki features option present in the admin dashboard. But now they are not.
I believe you are referring to AJAX polls when you say "before", is that correct? AJAX polls are a completely different feature from Discussions polls and can still be toggled on/off via the method you mentioned. Unfortunately, as Fandyllic said, there is currently no way to turn off Discussion polls. However, perhaps you could explain your situation to staff and suggest that they consider adding a similar toggle for Discussion polls.