That's my story too, felt like leaving after a year but ended up staying for 18 months. Even got a decent pay rise, and managed to change things a little, but the enthusiasm faded quickly, it was a dead end.

The day I stepped up and tried to set everything straight was also the day I decided to quit. Fast-forward a few months, I'm earning 2x as much, and working with everything I wanted to.

I too thought I was indispensable, but the company you have in your head can be very different from the managers'.