I'm in a minority who think yanbu, at least for the most part. I do think it is a step to far to tell her she is boring, or boring you with her chatter. But I do understand entirely why her obsession irritates you and bites harder because of the whole working-mum guilt thing.
I do think that children have over-engaged in their online lives during lockdown, at the expense of finding a balance of activities. Many children have frittered away huge chunks of time, with nothing to show for it. Watching anything is passive. Sure, you might learn a few things. But it is not healthy to do it ALL the time.
It is a very addictive activity and very hard for a parent to say no, when the alternative activities are not as enjoyable. We have battled to control iPad hours with DD age 10 during lockdown, setting limits has helped but then she will whinge about being bored, and needs interaction to get on with other things. There are only so many hours in a day a 21st century child will spend doing puzzles, reading, playing with toys or jumping on the trampoline alone. They know there are better things on offer - the ipad is irresistible.
I do think our children have been lonely during lockdown. No friends to play, no clubs, no grandparents, no school or shopping trips or playgrounds for ages... it is any wonder they enjoy listening to people nattering about nothing online? These youtubers become like friends to them.
I'm lucky that apart from watching cats on youtube, my DD hasn't bothered with it much (she has Disney+ and Netflix if she wants to veg out watching nonsense).
Her particular poison is gaming. Minecraft is a fading passion, and I quite like it but as she never played the aggressive version it was really just online building. She loves Roblox (I have a different take on this to you, OP, as I have permitted her access to the chat function so she has spent hours playing with her schoolfriends and cousins and it has been like a virtual play date environment. And I've found it very creative and imaginative - designing houses, exploring worlds, dressing up, caring for pets and children, doing talent shows etc. Plus it introduced her to coding as she started to do her own games, with some help from me and - haha - as few YouTube videos).
I would suggest you carry on humouring her and trying to divert her. But don't offer her books or baking!!! Meet her halfway. Tell her, okay she can tall to you for a few minutes about her fave YouTuber but then, you are DESPERATE to tell her all about something you have seen. Then, interrupt her and have something up your sleeve - maybe it is a YouTuber who teaches you how to draw cute cartoon characters, or a YouTube video that will make her laugh. Or introduce her to music! Get her listening to all sorts of different music online and find out what she likes and hates. Challenge her to build a playlist of songs that she can dance to, songs that make her feel happy, songs that are older than you are, etc (Those American Youtubers who video themselves listening to classic songs are also quite funny, she might like that.)
I'm sure you are bright enough to find things that are stimulating online. My DD happens to love watching clips of horrific weather events - there are some fantastic YouTube channels that do nature and science videos so I push her in that direction. Sometimes I challenge her to find out a fact that I don't already know about a topic (eg I say (untruthfully and with a huge smug grin), "oh I know absolutely EVERYTHING about volcanoes. You couldn't find anything online that I don't already know. I bet you a packet of Haribos you can't find a single fact about volcanoes that impresses me."). Kids love showing you that they are cleverer thank you think, and that you are not as clever as you think, in my experience.
I do think it is a mistake not to engage in these new ways of interacting, because this is the world our children live in. This is their reality. And, they are far more likely to give it a go when you suggest something, if you have established that you understand what they enjoy. I am now able to say to DD, after 5 months of persevering, 'hey time for you to have a screen break and do something different...' and mostly she now respects that (with a bit of eye-rolling).
Also, you can say that now she is back at school there will be no YouTube until x o'clock, and limit the hours at the weekend. She will moan at you, but that's fine. Tough it out. It is definitely in her interest to re-engage with what's happening IRL, beyond just what's happening online.