Ukraine would solve nothing in the Russian economy.
Ukraine would simply secure two things: Crimea (which is essential to Russia and was strategically exposed), and complete control on all main gas infrastructure towards Europe. It's not a coincidence that the invasion was launched when it became clear that the new gasduct to the North was dead in the water (because of American opposition to it): Putin wanted to make gas furniture to Europe strategically independent from other countries (i.e. completely dependent on Russia), one way or the other. The original calculation was probably "You don't give me Nordstream, so I'll take everything else". Obviously it didn't go as planned.