Simply believing in something doesn’t make it viable. You have to look at the history of cooperatives, how they operate under capitalism, and how they fare against capitalist companies. People have been trying to achieve what you’re proposing for many decades with little to show for it. You need to address why that is and why you’re so convinced that it can be different given all the evidence to the contrary.
The other aspect you need to consider is that capitalist companies will always have an advantage over cooperatives because they are much more willing to exploit the workers. The willingness to exploit allows the company to increase profit and market share, so competition fundamentally favors such companies. While you could argue that workers would prefer to join cooperatives, reserve army of labour ensures that there are always enough workers to go around. And of course, traditional companies can always temporarily improve their working conditions to run a cooperative out of business. We even see this dynamic with traditional companies competing.
Meanwhile, competition is perfectly possible under the communist model. For example, USSR had plenty of different design bureaus that would compete with each other. The difference was that it was friendly competition, and results were shared. The system was more efficient than capitalist competition as evidenced by USSR leading the space race.
Communism is prevented by people buying into the current capitalist model. Traditionally this has been the case because the standard of living in the west was relatively high due to the fact that most brutal exploitation was done in the countries the west subjugates. However, we are now reaching the stage of capitalism where exploitation is turning inward and people in the core of the empire are seeing their living standards deteriorate. As this process continues going forward, more and more people will reject the system.
Communists understand the inherent self destructive dynamic of capitalism and that you can’t just paper over these problems with cooperatives.