Sure, I didn't say you shouldn't write. There are plenty of people who write great code and then write about it. The author of Redis author has a great blog, where he explains various design and implementation issues. That kind of work may not qualify for most academic journals. But it is a lot more valuable than a lot of academic research and should be a valid way to get a Ph.D.
Is what he is doing scientific reesarch in computer science? Possibly, if he also writes up his results to that they can go into the scientific literature. If he does that, he can get a PhD.
A PhD in CS does not mean "extremely good software engineer," it means "scientist."
