EEE assumes open source software is only going to be created if it is widely used. As soon as that isn't true, it is irrelevant.

It was effective against companies that relied on interoperability and profited when people used their software projects. On the other hand, if someone wants to add features that my project can't support, it changes nothing about my life or work.

When the goal is "make the best software possible", the $MegaCorp would only compete by making software that is better that what is available in the open source ecosystem. That doesn't take anything away from anyone else. It is a Pareto improvement: people can pay and have even better software, or not pay and use the still-good free option.