You have picked a 1. random unpopular youtube channel (which might be good, I couldn't verify anything from it, as I couldn't find who ran it, if you know I am happy to be proved wrong) and 2. A disbarred barrister https://twitter.com/markgaleotti/status/927087181532991489?l.... There is much better information to pick than this! Any information will have a bias, and if they claim to be neutral I personally get suspicious of what that bias is.
Your assertion that you can't see anyway for Ukraine to win is based on "If Russia loses, it would be the end of Russia". Well, if Ukraine loses it will be the end of Ukraine, so I guess by your logic Russia can't win either? (TBF, everyone losing to some degree is right with war).
I won't get drawn into a discussion about how the war will go. People qualified to make a guess have been wrong and wont make prediction. Neither of us is qualified, so I will not be weighing in on this except to say that unexpected things happen all the time in conflict.