But Poroshenko and Zelensky were elected constitutionally, so your argument fails.
But let's drop the pretense. The "people" of Donetsk, Luhansk, and Crimea did not separate from Ukraine. Rather, small bands of Russian backed militants seized the territories. And given Putin's track record with elections, portraying this as a defense of democracy is laughable.
Without the participation of Donetsk, Lugansk and Crimea.
The elections your cite never applied to the oblasts. And, now, they are part of the Russian Federation and will never be part of Ukraine again. Deal with that fact.