With Russias statement that they have finished their first phase of the operation and will now focus on the Donbas, I think it's possible we may be seeing Russia "fold" and try and get away with more minimal gains since they lack any good options for achieving an outcome favorable to them. A hypothesis put forward by Michael Kofman suggests this, but he does caution that this assumes Putin understands the military reality of the situation, which is very much up for debate. Perhaps it's a more realistic (optimistic) scenario then assuming Putin will resort to chemical or nuclear weapons to achieve some sort of results.
Its notable that Russia has accomplished numerous secondary objectives in this war, such as restoring water access to Crimea and creating a land corridor between Crimea and Russia. While it's questionable that Ukraine would ever cede territory to Russia, these are gains Russia could justify to itself as "victories".