If the decision has been made to not use the search of previously browsed sites as the primary search option (as is the case in Chrome), then I would suggest at least search and suggest bookmarks before suggesting generic domain name. In the example above, I have youtube.com/feed/subscriptions bookmarked, but the first result is still youtube.com
So, this is how the system is supposed to work, we autofill "to the next slash", thus you could potentially do "y(right)f(right)s(right)" to go to your url. I admit for people coming from other browsers doing url autofill it's not the best experience. Autofilling urls would be a lot more expensive for us, and in some cases it would do a worse job than autofilling origins (it really depends on the site). An idea I suggested in the past was to use additional data from Adaptive History to autofill urls, that would at least be a stricter set of urls interesting to the user. I actually thought we had already a bug on file, but I can't find it (feel free to dupe if someone finds it) so for now I'll confirm this as an investigation target, because it's a quite common request.
I am using several sites where you have to go to their main page and press a seperate login button to be able to login. In Chrome I deleted the main page from suggested links in the search bar so the login page was the only one appearing in suggestions, making it faster to access the login page.