They can probably take Ukraine if they want it badly enough. But they will have to destroy every city and turn it into Gronzy. Capture civilians and deport them to Siberia. So that will encourage them rest of the population to flee to the West. Mobilize reserves. Take another 100,000 to 200,000 casualties this year. It can be done but I don't think they have the stomach for it. It was different with the Nazis, they were trying to wipe out the Russian civilization. This is not the case here. Unless Putin turns into Stalin. He's a dictator and ruthless but he's not Stalin.
“They can probably take Ukraine if they want it badly enough.”
Yeah, they’d have to go Grozny on Ukraine. But, Grozny was just a city, and Chechnya is nowhere near as large or formidable as Ukraine. Putin would probably have to go nuclear to lay total waste to Ukraine, and I doubt he would do that. Hell, I doubt seriously the Russian people would put up with it.