https://www.hoover.org/research/5-questions-stephen-kotkin
He believes, and I agree, that it might be enough for Russia to have "ruined" Kyiv, etc., and to have significantly degraded Ukraine's military. And, militarily speaking, Russia lacks the precision weapons to do much else. Put another way, I think Russia has made its point, that perceived (or contrived) threats on its border will be addressed. One hopes, having made the point, they will withdraw; otherwise Putin is facing regime change or worse IMHO.
EDIT: I should probably add that Russia has a point-of-view on Eastern Europe that shouldn't be ignored. Not as a justification for its invasion, but as a legitimate security and *influence* concern. Much was imposed on Russia after WWI, after the Kosovo conflict, and after the fall of the Berlin Wall. Again, not an invasion justification, but an important consideration for a lasting diplomatic resolution... that doesn't require further fighting, escalation or heaven forbid WMD use.