Yeltsin would have preferred a refashioned, democratic Soviet Union. But without Ukraine it would never work. The dissolution of the Soviet Union was not something Russians wanted. In those days, they had to make the best of a bad situation. I disagree with Gorbachev about Belavezha in one respect: it was not the cause of the USSR’s collapse - it turned out to be at the time the most prudent way available to manage tha collapse and none of the politicians at the time could have stopped it. The human cost of reversing it was simply too high. And that’s where we are today. Its impossible to reverse the new reality it created and no one really wants to restore the USSR even in the form both Gorbachev and Yelstin envisaged.
The Lithuanian argument was that it was not required to legally secede from the USSR because it was never legally incorporated into the USSR.