What will kill the planned economy is computing and communications. Once the people has access to mass communications then they will know that the West can (not for everyone though) deliver a better life. And the system crumbles.
China's totalitarian state works because it games the Western system and wins enough to keep the bulk of its people content. If the USSR is wedded to its ideological purity then unless they go full on North Korea they can't maintain their system in the face of global communications.
I am not sure if this is true. GDP per capita in the Soviet Union by the 1980's was on par with China today, and while it was quite unpopular in places like the Baltics, that was not true in Russia itself. The CPRF (successor to the CPSU) gained a plurality in the Duma in both the 1995 and 1999 elections and nearly won the 1996 Presidential election, and
a large majority of Russians even today state that they regret the fall of the Soviet Union. The Soviet Union was finally dissolved by a vote of the already existing government, not because they were violently overthrown (outside of the peripheral regions already mentioned) or because of a popular vote to abolish it in the republics which had not already seceded.
The USSR also never faced large-scale popular unrest in Russia after WWII - in fact, the worst unrest in Moscow since 1917 was in
1993, when the "democratic reformer" Yeltsin illegally dissolved the elected Parliament (which was dominated by pro-Soviet parties) and sent the military to retake the legislative building (which was defended by anti-Yeltsin civilians) force, resulting in over a hundred deaths. Much of the unrest present in the late Soviet period was in fact coming from more extreme communists who were upset about the more moderate position the government was taking, i.e. the
Storozhevoy mutiny.
As there was not much violent, pro-capitalist unrest in Russia OTL, I don't think it's super likely that the advent of Internet (which would almost certainly be censored like it is in China anyways) would cause so much that it would overwhelm the Soviet armed forces. If anything, they would get a less positive view of the West than they had OTL in the late 80s, where they saw Gorbachev visiting a fully-stocked American supermarket but not a homeless encampment, while the Internet would show both.
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