I'm not under the impression that "the same system we have now but a bunch of worker coops" would be some kind of ideal society, but it's far and away a better business structure than the ones we have now.
What are the barriers to successful coops being established?
I agree with other comments saying that some of it is just ideological, but another big reason is that it's extremely hard to compete with large chains price-wise, especially if you are in the groceries business. So you end up catering to well off libs with a guilty conscience or go out of business. Chains and monopolies play dirty too and can fuck with co-op's supplly chain by bribing or threatening suppliers.
Presumably that would also apply to capitalist small businesses though
Indeed it does.
There are even more hurdles for a co-op though if you wanna pay everyone equally and well instead of exploiting the shit out of workers.