In ideal world. Stuff like groceries are such a rigged market that (well I'm sure somebody already wrote a book about it, recommendations?) it puts financial institutions to shame. Just a few brands own most of the stuff you buy [1] and then supermarkets have deals with those. Both protect each other.
I mean market finds its way, people can move to small stores and non-branded products if it gets bad enough, but to paraphrase, market irrationality can outlast people's well being.
I'm not in favor of some more regulations which usually only help big players, but corporations power steadily climbs and I expect it to become bigger than those of governments.
New big companies, some decent competition, come from places when there was none. They hardly ever can push themselves into existing markets. They create new ones. But we still need groceries, gas, electricity etc.
1. https://www.reddit.com/r/coolguides/comments/elzqf2/eleven_c...