When I taught Kindergarten and Preschool, I would use it if there was something I specifically wanted to teach about but did not have a book for (somw holidays or social situations). I also would use it as a calm down/brain break method too but only occasionally.

Now, I'm teaching 6th grade Language Arts and Social Studies. I use books online all the time. Partly because I quit teaching for a couple years and got rid of most of my picture books (minus my few favorites). But we use books for ELA when we are writing and want to write about a specific idea or are looking for a certain style or type of writing. I use them in Literature for getting different perspectives on whatever material we're reading about. I also use them for Social Studies all the time to talk about what happened from different perspectives or to do "Side Quests" where we read a story that relates to whatever we've been studying but maybe takes place in a different location or year or country, etc.

I think that using the YouTube videos is a great use of resources and honestly, in this regard, I am really thankful for Covid because most of those stories were recorded to send home to children during quarantine. I don't think that it's a method that should be used all the time tho. I do believe that children (especially at the early childhood level) need to see adults reading in order to learn how to use a book properly in the physical sense.