I disagree with this. No, I don’t think Russia wants to ‘annex’ all of Ukraine per se, I think the original goal was to invade, quickly topple the government, then set up a puppet state which would be subservient to Russian interests. This would perhaps be combined with an annexation of much of the east. It was set to be a more successful version of Georgia 2008 (which from an operational level was a bit of a screw-up, but Georgia was weak enough that it went well enough anyhow).
Ukraine had signalled its willingness to stay out of NATO before the invasion started. Access to the Black sea was definitely an issue but not the primary war goal, hence why Russia initially directed its most intense attack towards Kyiv (it was not a feint, Russia dedicated a huge amount of manpower here and made an earnest attempt to sweep through the capital here). I think it’s pretty obvious the Russian government doesn’t care at all about ethnic Russians/Russian speakers as this war has made life a hell of a lot worse for most of them. Plus the accusation of ‘genocide’ against the Donbass was vastly exaggerated and a clearly cooked up justification.