YouTube, Twitch, Crunchyroll, Netflix and various other video streaming sites, what kind of web development skills are companies like these are looking for?
Google (YouTube)/Amazon (Twitch)/Netflix normal minimum qualifications for FE dev roles generally seem to be BA/BSc in CS (or equivalent) + HTML/CSS (and I guess AJAX) knowledge + strong knowledge of a programming language (JS/Python/Java commonly) + some experience of developing web applications. There will be nice-to-haves in the job spec that are a bit more specific, but they are nice-to-haves. No idea re Cruchyroll but it’s owned a similarly ginormous mega-corporation (AT&T), would assume similar without looking at the job spec.
Edit: this seems like I’ve ignored the question, but I haven’t. The companies you’re talking about are massive, with multiple products (released and unreleased) and vast cash resources. They can hire someone who is very good at using one programming language (not necessarily JS!) + who has built web applications (so has knowledge of the problems) and train them up. If you have very strong general knowledge of principals, then the specifics of some random framework or API are easy to teach, vice versa not so much.
(Contrast this with a startup or small business that is in the business of video streaming. They need someone that knows (or can very quickly learn) a specific set of tools. So for frontend, has to be JS, ideally needs to be the specific FE framework the company uses, ideally needs to have already worked with streaming so they understand the problems, ideally some backend work related transcoding/optimising/transporting videos, etc etc. These companies can’t just hire someone and have them be non-productive for any length of time.)