What Ukraine needs is not what NATO needs, NATO does not need a war with Russia as has been made abundantly clear by NATO leaders.
Also joining NATO is a privilege that a country must earn through certain criteria: Every NATO member from Eastern Europe spent many years reforming, dealing with corruption etc. Ukraine has not thanks to oligarchs like Poroshenko.
Perhaps if Ukraine survives this war and Zelensky actually implements the necessary reforms, but absolutely not now. Same with Ukraine joining the EU.
Assuming they take Mariupol and the LOC ( the heavily fortified front line in Eastern Ukraine from 2014 till the war started in February ) quite possibly they will work to take places like Khrakiv and Dnipro.