Depends on who you ask - I'm fine with it and haven't said otherwise. What is a problem is when one person profits off the work of another (as in, pays them less than their fair share), which is basically all salaried employment.
If the co-op is sold at a profit, and those profits are distributed to the workers (who obviously all put in the exact same amount of work and time, right?) then they are profiting off the work of others, aren't they?
For starters, not everybody in a coop has to earn the same amount or get the same payouut from a sale. They just all need voting rights. The point of cooperatives is to be owned by all their members, not just the founders.
Second, yes the profit in the marketplace is still exploitative to a degree, but we don't have a viable alternative so there's not much to do about that. I don't believe there's much point critiquing something when there's no alternative.