I'll agree that everyone and every job
will be at least slightly different.
Ideally I guess everyone would be paid like gymnists or skaters are graded, on difficulty and excution.
I guess my problem is I've seen and talked to too many in factory work in the past that saw individual supervisor appraisals mean different rewards, but not based exclusively and sometimes not even mostly on merit. Also when layoffs were done by pick and choose it was too often who you know not who deserved it best.
I worked with a man that was a real go getter, worked hard, did his job the best he could and fast as he could. Our boss appreciated his work, but the guy's attitude was terrible because he had gotten laid off from another job while people that he at least considered unfit to work even didn't. It wasn't even by senority, it was who was the supervisor friends. People other than himself agreed, at least some that I talked to. But this was the same boss that gave one guy the raise we didn't even know was available to ask to receive I mentioned earlier. Overall a good boss, but still there was that problem with the company. To be fair, I've always suspected a couple of management outside of maintanence somehow got the guy in question the raise more than his supervisor. After working with the industrial engineers on a couple of projects, the electrician in question began to spend more time in their office than doing his job.
I can deal with someone doing similar work but only what they absolutely have to getting the same pay better than I can deal with someone doing only what they absolutely have to and getting more pay. In just the small shop group I work with every day there are a couple I'd have to rank more valuable to the company than me, several I'd put us equal, and one or two that the company would probably be better off to replace.