I do a lot of 'proceduralised' jobs, but I'm 'lucky' in that I get to define and hone the procedure and then it tends only to be necessary for a few hours or a day or three, before I move onto something else entirely. I get a wee quick out of making things more efficient, then get to move on before my brain calcifies.
The thought of acting a mere part of a machine for 8 hours a day, weeks, months and years on end is ... well, it makes me appreciate my job, even at its worst!
Interestingly, Toyota's factory culture is very different. It's part of company philosophy to seek continuous improvement. They're also big on cross-training and investing in staff. Basically, they respect that hands come with brains, and that it's worth engaging both. I suspect I would have enjoyed that much more. If you're curious, the This American Life show on NUMMI gets at the contrast between the two approaches.
[1] https://en.wikipedia.org/wiki/Flash_(manufacturing)