Seize the means of production comes from a conceptually separate part of anti-capitalist critique then workers' control/workers' self-management. It is common to conflate these two strands of anti-capitalist thoughts. It is technically possible to have common ownership of the means of production without workers' self-management and workers' self-management without common ownership of the means of production. Universal worker coops only requires abolishing wage labor not private ownership @memes
Property's moral basis is getting the positive and negative fruits of your labor. Capitalism denies the workers this as the employer solely appropriates the positive and negative fruits of their labor. The core of property's moral basis is the principle that legal and de facto responsibility should match. Receiving wages is not sufficient because the workers remain de facto responsible for the whole (positive and negative) product of the enterprise and are entitled to it on that basis
It doesn't have to work like that. Instead of capital hiring labor, labor can jointly hire capital and structure the firm as a worker coop. There are good ethical reasons for organizing production in a worker coop as well
On the part of labor. No matter how causally efficacious capital is. It can never be de facto responsible for anything because responsibility is imputed through the tools back to the workers using them.
A better case for worker cooperatives is just pointing out they satisfy the moral principle that legal and de facto responsibility should match. The workers are jointly de facto responsible for using up the inputs to produce the outputs, but in a capitalist firm, the employer holds sole legal responsibility for 100% the corresponding legal claim to the positive and negative result of the enterprise while employees receive 0%. In a worker coop, this mismatch is corrected
Even if we ignore the artificially increased transaction costs and hold out problems associated with private ownership that make acquiring means of production more expensive, this point only justifies some sort of compensation from the workers as part of the negative fruits of their labor in production. It does not justify the capitalist appropriating 100% of the positive (legal right to produced outputs) and negative (legal liability for the used-up inputs) fruits of the workers' joint labor
Under postcapitalism, the factory would be commonly-owned. The company that operates the factory would worker-controlled. That being said, there is nothing wrong with the holder of the building even in common ownership setup being compensated. What is unfair is to demand control rights over the firm for this capital and make the workers at the company your employees. Not everyone against capitalism is a communist. There can still be economic incentives for productive activity