Sure, Putin has been able to throw enough troops into the meat grinder to advance a few miles here and there. But it's a tiny percentage of the country. For perspective, they just captured Avdivka. It had a prewar population of 35,000. Russia lost 40,000 casualties to take it.
Just maintaining those conflicts indefinitely would prevent Ukraine from joining NATO and would have attracted a lot less international attention to Ukraine. It also would have been a lot cheaper in terms of economic sanctions and military losses.
I doubt it will happen. They have a ton of natural resources. The oil and gas corps alone can hold the entire economy afloat (Gazprom, Lukoil, Rosneft) and fund their tanks and missiles.
One of Ukraine's goals with last year's offensive was to sever the land bridge. That objective failed. Ironically, Russia (likely) blew up the Kakhovka dam to slow down that Ukrainian offensive and thus severely restrained water access to Crimea (which they had fully reestablished in the early days of the war).
He feared wealthy, comparable countries nearby, exposing him as the incompetent chief of thieves he is.
Having failed to accomplish the easy win, there's no way to back down and say, "Well, never mind". He still desires the emotional goals of owning that land, and having sold it as an existential risk against NATO, he can continue to get support at home.
Which will last as long as he can continue to staff it with prisoners and disfavored ethnic groups, and various countries continue to fund it by skirting sanctions.
This series was written 8 years ago and predicted another invasion of Ukraine.
The tldr is it was a strategy for Putin to remain in power.
There will be no peace with Putin but a military defeat may be enough to get rid of him. So I don’t really understand at all why Europe and the US are so hesitant when this is a way to obviously damage Putin.