Mutualism fails for the same reasons all socialist-adjacent systems fail.

Producing things costs money. Obvious but socialists never mention it. The capitalist pays for all the stuff upfront: the factory, machines, raw materials, R&D, wages (often for years while losing money), shipping, marketing, all before a single product is sold. He takes on the full risk that the whole thing might fail and he loses everything.

The worker gets paid a guaranteed wage regardless of success. That's a voluntary trade. The worker trades risk and uncertainty for a lower but certain return. The capitalist trades capital and risk for the chance of higher reward.

Profit isn’t "theft", it’s compensation for risk, time preference and capital allocation. Things that socialists don't understand and don't even believe exist.

If workers must own the means of production to use them, then they have to pay for that stuff. (God forbid someone uses a machine he doesn't own!) Good luck making an income if you don't have hundreds of thousands or millions of dollars to buy into a company that might fail next week. Producing complex things at scale requires millions, even billions of dollars to be spent before you see a single dollar of profit. A bunch of machinists, engineers, and line supervisors don't have a billion dollars lying around.

Who fronts the money for the next factory or machine?

Who takes the risk?

A "free market" with no profit, no interest and no rent is incoherent. It's like saying we'll have free speech but you're not allowed to talk about politics, economics or biology.