That is absolutely correct. And this was known (or should have been known) before this counteroffensive was planned. So now, why do we still see the Ukrainians marching in these open fields and being sitting ducks in these very flat lands that you are talking about? Seems dumb. Seems evil to pressure them to do that.
You see, you just revealed the truth and I know you know this... but in Donbas in the east, the Ukrainians had heavily fortified positions in these industrial/urban areas that provided plenty of cover for them to nest in. That is why it took so long for the Russians to root them out. But now, in this counteroffensive near the steppe of the Dnipre River east bank, now you have open fields that don't have hiding places.
Poland and Romania to a far lesser extent.
Everything you say here is true, yet you refuse to acknowledge that the US/NATO encouraged the Kyiv Regime to poke the bear anyways, in spite of the clear advantages that you point out right here. Instead of poking the bear, Ukraine could have unilaterally been able to broker a peace deal with Russia and still maintained their sovereignty. But Ukraine lost its sovereignty in 2014 after Maidan and became the 51st state or 31st member of NATO. Instead of Ukraine being able to be a bridge between the West and Russia and getting the benefits of both, the US came in and pumped them up with these crazy illusions of beating the Russians with the backing of NATO. And it simply isn't coming close to working.
It really angers me that you can say what you said here and be fully aware of the situation, but because of your ideological biases and hatred of Russians, that you would support the Ukrainians dying in industrial numbers in a war you clearly admit is unwinnable for them.... and you are in denial, again because you are ideologically driven, of the fact that NATO cannot win a (conventional) war against Russia at this moment in time because we don't have the production capacity or the political will to put boots on the ground from NATO member states. Outside of nuclear, the only other option NATO has is to convince the Poles and Baltic States to jump in, but not under the cover of NATO which might trigger Article 5.