Ukraine has ZERO chance of gaining back any territory. Tens of thousands of Ukrainians have already died. And, Ukraine is shrinking. All that will continue unless it unconditionally surrenders.
Because "unconditional surrender" is what every country does when it is trying to retain the territory it still controls.
That's just a bad joke.
In any case, the decision whether to continue fighting is up to the Ukrainians, just as our ancestors' decision whether to continue fighting against the British during the Revolution was up to them.
If they don't want to surrender and return to living under the bootheel of Moscow, that's up to them.
Your overused analogy would only work if the French had arranged a coup in Philadelphia, installed a small group of pro-French radicals, who started killing British sympathisers, while banning all things British, in an effort to join a political union with France, while paying off relatives of the French king to keep the money and arms flowing