Far left libertarian here, meaning that I support market socialism and many of its attendant policies.
Quick point of correction: this grocery store isn’t socialism, not in the sense that Marx defined it! (Nor are this town’s water utility, power utility, etc.) These are all simply public goods: commodities and services that are provided without profit to all members of the community.
The heart of socialism is a belief that the labor force should control the economic means of production, i.e. the capital. In Marx’s industrial age, this meant that workers should own factories, tools, distribution networks. In our time, “capital” is more fuzzily defined; many people use that word to mean “money,” but money isn’t a means of production by itself.
In the information age, most property is intellectual and socialism is best exemplified by worker-owned businesses, profit-sharing businesses, and a few degenerate hard-capital cases such as good old factories, electricians who own their own tools, and other self-employed people.
So, by all means, let’s celebrate the creation of more public goods and teach our benighted right-wing peers why they’re wrong about government-sponsored businesses – but let’s not confuse public goods with socialism, else we risk losing sight of the actual value of socialism and simultaneously making public goods harder for the right to swallow.