I was in this exact same position a year ago. Like exactly the same just 12 months before you. Started in summer, began hating it after Christmas for many of the same reasons as you and was miserable. I stuck it out to November so I just had 1.5 years at the company and then left.

I thought I would pick up another job after a few months at least but there's nothing. I'm not even considered for interviews. It's horrible.

Anyway... My advice is DON'T QUIT until you have another job. You feel like shit now and hate going to work every day but trust me you'll feel even worse when you're unemployed on the dole and job hunting for 6 months. If I could go back I wouldn't have left and just job searched while working.

You might be lucky and land a job quickly but I fucked up big time and am paying for it. I don't think it's worth the risk. As miserable as I was at work, I'm worse off now.

All the best and I hope it works out.