Russia is taking this veeery slow. At some point Ukraine's best forces in the Donbass and Kharkov will be at risk of encirclement, but at this pace it will take a long time. In the north the Russians haven't consolidated their hold in the eastern route to Kiev, either, but ISW claims they've brought reinforcements for a renewed offensive on the capital in the next days. Spending more time isn't good for the Russians, on the short term there's more mud on the roads, and on the mid, the economic impact of sanctions will continue to be felt and warmer weather will make Europeans less reliant on gas. I don't think a slow invasion was on the Kremlin's plans, the timing would be off. They probably miscalculated enemy morale and expected a quick takeover.

The more Ukraine puts up a cohesive war effort now, the more of a real nation it becomes. It's feeding an us-versus-them sentiment and a national myth and the memory will linger on in the future pro-Russian regime in Kiev. How wide the sentiment gets will depend on the fight now (maybe there'll be a breakdown and shock at some point) and the competence of the future regime. A quick breakdown of resistance and Russian takeover would've severely demoralized the nationalists, but that opportunity has been lost.