What would you do if you were promoted to a job you hate?

I’m two months into a three month probation period of a job I hate. There’s very little difference between the jobs in the money respect, the hours in the new one are marginally worse but again not much in it. It was an internal promotion. In the old job I was actually in charge of a (small) department, now I’m just a middle man in charge of not very much at all. The old job was more customer facing but also more procedure based, as in it was “all these things must be done daily and all these things weekly”. The new one I’m more in charge of people (I think) and the admin things are just laughable. There’s one task I have to do weekly, I said to my boss I wasn’t very comfortable doing it to which he said “ok I’ll get someone else to do it” (!!!). I was more looking for some guidance in how to do it, but instead it just got taken away from me. There isn’t even any pressure to do anything at all, I could sit on a computer playing minesweeper for half the shift and nobody would notice. I don’t have any input into the old department anymore, despite the fact I’m by far the most experienced one at it. I feel like I’ve sort of been shuffled out of the way a bit. There’s no progression from the old job (well only to my current one) but the job title of the new one is fancier and there is some progression from that. But to be honest I don’t really care, I don’t want my bosses job, I don’t even want my current one! I’m worried I might be thinking the grass is greener, but equally worried it’s that thing where people get promoted just past their level of competence and I can’t see that I’m incompetent. Should I go back to the old one, or try and mould my current one into a job I actually like? Talk to my boss? I dunno. The other thing is that if I demote myself the person likely to get my job is an imbecile. Then again it seems easy enough for an imbecile to do! Anyone been in the same boat?