The fallacy here is that a Walmart cashier job is inherently unenjoyable. I see no reason why that should be. Some people are suited for it and some are not. This comes very close to that stupid phrase “first world problems.” Look, I am the son of an immigrant who grew up in the third world. She worked hard her entire life. Some jobs she hated, some jobs she loved. But if she hated a job, she moved on when she could. All were jobs you would probably disparage as requiring some sort of mental jujitsu to overcome. But the truth of the matter is that my mother worked until the age of 78, when arthritis forced her to stop, and she has been depressed ever since. Work (cashiering at a restaurant, actually) gave her life purpose and joy. She loved socializing with her customers and now that has been taken away from her.
But your point about some jobs being like a cancer is valid. I had a job like that. I made a lot of money doing it. To most of my peers, I was a success. They thought I was crazy to walk away right at the time the financial crisis hit. I endured more than a year of unemployment. Now I work twice as hard for half the money, but I like what I do and I can honestly say I am much happier. My friends and family think I’m nuts but I couldn’t care less.
Recently I had to house sit for a friend who has been working a job she despises for 20 years now. She has a very nice house. Living in that environment for two weeks showed me the life I could have had, had I remained in my job. The life I had always expected to have. Is she happier than I? Who can say? But I have no regrets. I tend to think that if your job is a cancer, you can find something that suits you better. And I think my mother would agree.