That's really the crux of the matter here. What is Russia's goal here? If you're operating on the assumption that they indeed want to capture the entire Ukraine, it then indeed looks like they aren't doing as well as a lot of people seem to have expected, thus far.
However, it's possible that Putin is using the Russo-Georgian-War (2008) playbook again which didn't aim to capture the entire country, with the goals of ultimately capturing only some of East Ukraine (Dombass in particular, and keeping Crimea) and forcing the remaining Ukraine in negotiations to become a "neutral" state located between Russia and NATO/EU. While again embarrassing the West and their military and diplomatic resolve as a cherry-on-top. That Russia has been hitting targets in the west of Ukraine might have been to destroy Ukrainian military's capabilities and capacities, in this scenario.
Even if it's the Georgian playbook again, I still think Putin might have grossly overplayed his hand there. The NATO and EU will likely not let go as easily this time, especially not because in particular Poland, the Czech Republic and the Baltic states as NATO and EU members feel very threatened and expressed themselves as such.