I'd be ok losing youtube. There's some good content there, but there's so much garbage and I can only hear people begging me to like and subscribe so many times. I've got more dvds and blu-rays than I can watch, and there's so many at good will too.
All I get in gmail is transactional mail for other people. It would be no loss. My personal email is at fastmail, and I'd expect them not to participate in the browser in browser thing, but if they do... That's fine. Email isn't that important anymore. What am I going to miss? If you want to contact me, send me a letter or call me or text me or ... ?