Yes, that certainly is a good point but what can be done now?
Right now, the Russian army is in Ukraine killing Ukrainians and destroy Ukrainian stuff. They are bravely fighting back, but, as in all wars, it is the people who suffer.
There are many ways to end a war. It can be total victory for one side or the other or a negotiated settlement. I do not think the Russians or the Ukrainians will win a total victory over the other so that only leaves two options:
Continued death and destruction or a negotiated settlement.
Your idea certainly has merit from Zelinskyy’s side; but can it be achieved, or if it becomes a sticking point, will it needlessly prolong the suffering? The Ukraine joining NATO will be a big threat to the world in so far as possible conflict to include nuclear war with Russia that we all should not want.
The whole integrity of the Ukraine from postwar Russian hostilities can be readdressed at some future date.