If your project has kubernetes, some front-end framework, a database, etc., _someone_ needs to understand how it hangs together. I think it also _is_ possible to be deeply proficient in multiple technologies, but the problem is most people have neither seen nor experienced deep proficiency in even one technology, because they have never worked in one technology longer than 2 years in this environment, and everyone they work with is the same way. It's hard to get to a destination if you have no idea it even exists, much less no one you know has ever been there.