No. If you can't win, it's imperative you make sure the enemy doesn't win either.
This would be the part where Princess Luna should gets as many ponies out of Equestria as possible, then either destroy Changeling occupied lands with kilometers sized meteors, hopefully annihilating Chrysalis, most of the invading Changelings, and leaving any Changelings that survived NOTHING but ashes - or rebuild the Equestrian civilization from a secured location, say the Moon, and gearing it up for war, so it could one day return to Changeling-occupied Equestria, even if it's generations later, to reconquer it for the ponies from the Changeling overlords.
It's my belief that if the enemy poses a GENUINE existential threat to your civilization, culture, people and way of life, in this case being turned into a food source, when the alternative is either enslavement or extinction, and ascendance of the enemy to ultimate power, which a Changeling victory in my view would bring, then there is no middle ground, and ANY MEANS is permitted to ensure THE ENEMY DOES NOT WIN, at ANY COST.
Victoria aut mors - VICTORY OR DEATH.
Or, yeah, if you can't beat them, join them, and hope they would be merciful.
Then again, I guess I'm acting up again over the issue. it's just that after seeing some fan work on the horrific consequences of a Changeling victory in "A Canterlot Wedding", for example, this: www.youtube.com/watch?v=y-1dya… , I just really can't accept the Changelings, even for laughs.