Gorbachev himself is/was a believer in communism, although I can't find the source for it now.
So, he wanted to maintain the SU at any price, which was, due to inner party struggles and a fed up public, a duty he couldn't fulfill, all of his reforms came to late.
'Asked to name the things he most regretted, he replied without hesitation: "The fact that I went on too long in trying to reform the Communist party." He should have resigned in April 1991, he said, and formed a democratic party of reform since the Communists were putting the brakes on all the necessary changes.'
Although, in a specific sense, he really wanted to dismantle it:
'His second regret, he said, is that he did not start to reform the Soviet Union and give more power to its 15 republics at an earlier stage. By the time he began to think of creating a looser federation in early 1991 the three Baltic states had already declared independence. Blood had flowed in Lithuania and Azerbaijan in the Caucasus. Under its ambitious leader, Boris Yeltsin, Russia, the largest republic, was flexing its muscles and demanding more control over the Soviet budget. Some analysts say the whole Soviet system was unreformable and any change was bound to lead to an unstoppable process of increasingly dramatic transformation. It was inevitable, according to this analysis, that Gorbachev lost control.'