IMO it's got more to do with the fact that providing a power user feature such as "run a regex search on the closed captions" would implicitly define an API which needs to be maintained. It could complicate the backend forever or block certain optimizations even if the feature is used by a tiny percentage of users who'd be outraged when it's removed.
Any UX designer just had a heart attack reading that. Yes having a bazillion knobs and buttons is cool for hackernews folks, but as a user, it's just confusing. There's a reason iOS is so popular, and Pixel devices are creating an iOS like simple UI.
I do agree that 1-2 or the stuff mentioned above would be nice, but most of it comes off as a programmer trying to tweak the hell out of a system, ignoring that 99.99% of users actually won't benefit from ANY of that.
Being able to hide complexity can easily solve this problem. A user interface can come in multiple flavors. The default interface is typically simple and suitable for 95% of people. The other 5% need things like stats for nerds, advanced options, etc. Making advanced options limited defeats the purpose of advanced options. If you have too many casual users clicking through to advanced options, it means you did a bad job separating concerns in the first place.
But the question is, how much engineering hour and effort do you want to put into a feature that will benefit a very tiny percent of your users, vs putting that time into trying to make the experience that 99% of users have better?
What is even more confusing is having UI elements that don't work as you expect (not interested, dislike button etc).
The search on youtube is also completely broken, I have not monetised any of my videos and the penalties for that makes it so that if I search for the exact title + my channel name the video will show up on something like page 5.
Also, complex != confusing. You can have very simple UIs that are confusing as hell if you're not used to them or you need a specific issue. I usually have trouble helping my mother on her iphone because I'm not used to it and it has absolutely no guides or help functions if you can't find what you need. Usually it's a "magical gesture" that is documented on some obscure web page.
