I think this is very likely entirely true.
It may also be true that the war, even whilst being lost on the ground, is helping Putin. Polling seems to show unprecedentedly good ratings for him, his entire leadership publicly pledged loyalty to him and his war, and he's able to use it to further repress free speech and opposition. A long and bloody conflict to hold on to Donbas and perhaps the Azov coast land bridge to Crimea might be winnable for Russia through sheer force of arms, and from a perspective of reinforcing Putin's hold on power, be a triumph. Even if (maybe even especially if) it impoverishes the rest of Russia. There are plenty of examples (Saddam post Iraq war I, North Korea, Iran etc).
I will be making no predictions how this turns out. I've no idea.