I think you could be right. We might tell our grandchildren one day.... once upon a time there was a country called Ukraine. It is a part of Russia now.
On the flipside, marching on into Donbas alienated Putin from rest of Ukraine even more. The west side of it will never back down without turning it into a bloodshed. Putin isn't that stupid to orchestrate a full blown invasion(I hope) as the population there will oppose to be annexed and assimilated.
History remembers what happened in 2014 and the annexation of Crimea followed with very weak sanctions that was expected at the time too. Gradually from that time on Putin started feeding Donbas areas with separatists and propaganda to reach the point we are now.
He wants to bite off another area which will use as a cushion between a future NATO state and his borders, something that he already did with Georgia.
Sanctions however don't work straightforward, as some of what people are suggesting would at times mean that Europa would pay more as a direct consequences of the sanctions rather than it will hurt Russia.
Strict economical measures would mean heavy losses for all sides that are part of the equation. Maybe not USA which are far from the conflict zone and might gain advantage over EU due to the recent events.