Even if 90% of the product’s value was the Linux kernel (which I disagree with but I won’t get into it), the massive value that Red Hat adds to the kernel is a

Even if 90% of the product’s value was the Linux kernel (which I disagree with but I won’t get into it), the massive value that Red Hat adds to the kernel is a stable ABI for 10 years. Fixes and new features have to be meticulously backported while maintaining compatibility and stability. So yes, it’s community code, but with a huge amount of release engineering to get it to an “enterprise”-ready state.