I got my Chromecast like 10 years ago and have the same issue with YouTube casting. Netflix is also pretty terrible and only connects 50% of the time, but once it’s connected it’s good. It wouldn’t be so bad if it just let me cast my whole screen and not open some dumb app like with every other website.
The dumb thing is I can watch shows in HD issue free from a free streaming site on my pc but the second I cast it my internet goes to shit and I have to leave it on 720 or it buffers endlessly. I should just switch to the HDMI cable route but I don’t want a cord hanging across the floor, too many dogs.