I am personally completely unable to understand the decision to remove the ability for me to search a youtuber's videos. I didn't even know this was something a video website could take away!
It does exist but it's hidden in the tabs. My m1 mac screen is not large enough to show the search icon which I must click on the right chevron icon to see as it's on the far right.
I'm glad it's there but it wasn't always like this. I wonder if I'm just an idiot (totally possible), a dark pattern, or just a bad UI change.