To Putin and his gang, "denazification" means the elimination of Ukrainian nationalists who are opposed to Russian subjugation and the forced imposition of a pro-Russian government. And the only province that has a ethnic Russian majority is Crimea. Donetsk and Luhansk have Ukrainian majorities of around 60%, and Kherson and Zaporizhzhia of around 80%. This has been pointed out many times but is something that pro-Russian apologists assiduously ignore or deny.
The whole argument about reclaiming ethnically majority Russian areas is nonsense anyway. Would the USA allow majority Hispanic areas in the US Southwest to secede and be annexed to become part of Mexico?