For a company as large and pervasive as Google, many of their products have notorious problems with usability and, sometimes, accessibility. The concerns you raise here are legitimate. The lack of captions on the videos is not GC’s fault, though, it’s mine and the content creators’. I think the last issue you mentioned is the most important one in terms of accessibility. The GC interface has issues with discoverability.
For a company as large and pervasive as Google, many of their products have notorious problems with usability and, sometimes, accessibility. The concerns you raise here are legitimate. The lack of captions on the videos is not GC’s fault, though, it’s mine and the content creators’. I think the last issue you mentioned is the most important one in terms of accessibility. The GC interface has issues with discoverability.