I agree, all kinds of grocery stores have failed over the years. Kroger's just isn't a good example of a failing store for a lot of reasons. They aren't a stellar investment, but they are also up from 1 year ago and 5 years, so investor's don't look like they agree with your summary of the business.
https://massmarketretailers.com/kroger-delivers-solid-quarte...
They didn't lose money because of their grocery operations. Those margins have increased slightly.