Zelensky's offer is completely contradicted by the stated positions of U.S. policy makers for years since the 1990s. And those are closely tied to a long-held foreign policy goal of Great Britain -- dating back to the days of the Ottoman Empire in the 19th century -- to keep Russia from establishing warm water ports that would enable it to contend with the British Empire as the preeminent power in the world.
Nothing has changed in nearly 200 years except the U.S. has replaced Great Britain as the preeminent power in the world.
Zelensky’s offer was confirmed by Putin’s chief envoy to Kyiv. As for not having a warm water port, that is an accident of geography. Russia does not have the right to demand one because it would be a nice thing to have. Nor does it make much difference if NATO controls the Dardanelles.