Zelenskyy straight-up said Ukraine is going to lose if Congress doesn't send more aid
(www.businessinsider.com)
Yes, no shit. That was the outlook from day 1.
The Russian Army is largely represented as a bunch of baffoons in the Western media, but it's still one of the 3 largest armies in the world. Ukraine cannot hold their lines indefinitely, the only way to "win" against an opponent that has multiple times your materiel available is guerilla.