Avoid WWII and the Cold War as we knew it. The losses suffered, followed by crushing victory and an atomic staring contest meant you had a national leadership defined by paranoia, military chauvinism and a belief anyone who hadn't served in the Great Patriotic War wasn't good enough for a top spot. Which led to the insane position of pensioners on dialysis commanding a superpower. The Cold War in of itself, as it took place doomed the Soviets. The US had all the advantages for 'peaceful' competition - even if you hand waved Washington into a mirror-image Stalinist state, its resources and geopolitical position would see it through to victory.
Brezhnev out of the picture alone could probably give the USSR another decade of life, his complete indifference to rot and corruption is frankly staggering. Replace him with a competent reformer and political operator like Kosygin and who knows the USSR might not even have import grain(!). Its not doing a Deng but Kosygin, and fellow Leningraders had a bent for technocratic improvements and providing financial incentives, basically Tito-lite. However limited scope and Brezhnev's paranoia over the man's position meant he was consistently held back and limited to a seat warmer in the Politburo by the 1970s.
Actually a good POD might be avoiding Andrei Zhdanov's death from alcoholism in 1948 (have him follow Stalin's advice to quit the bottle). He rose in Stalin's favour during the war and quickly became the dictator's favourite showering him with praise and genuine paternal affection. He managed to get Malenkov isolated and influence Stalin into breaking up Beria's intelligence empire in 1946. Who knows given a few years, Zhdanov might encourage him to rid the Soviet Union of Beria entirely, frankly given Stalin's low opinion of the man its impressive he never did.
His death allowed Beria and Malenkov to worm back into favour and by January 1949 they played on Stalin's paranoia, drawing parallels to Kirov and Trotsky with regards to Zhdanov's lieutenants in Leningrad who commanded a relatively autonomous control of the city. Que the Leningrad Affairs which saw men like Kuznetsov shot, Kosygin thrown into the political wilderness and over 2,000 low level officials thrown into the actual wilderness of Siberian exile.
So say Zhdanov lives, Beria and co. are thrown out (possibly shot) and he becomes official successor. Stalin dies around 1955, and his loyal bureaucracy falls in line behind Zhdanov. The Leningraders, like Kosygin come to power with him and set about reforming the system as did in the Hero City, which basically boils down to depoliticising the economy, adding varying financial incentives, a technocratic approach (so no planting corn in Siberia on a whim) and an increased focus on light industry. In such a USSR I imagine no Secret Speech, and more subtle changes with the added benefit of Zhdanov and co. being the Man of Steel's chosen successors. I can also see Stalin in time receiving similar treatment to Mao in China, still visible in national imagery but a 'flawed hero'. He remains entombed next to Lenin, and Zhdanov might join them in time, say circa 1960-65 if he remains teetotal.
Its still a Stalinist hell hole in many respects but you get fewer bread lines, more productivity and if you avoid the various coup attempts in favour of succession, the MGB/KGB might remain subservient to the Politburo. None of this avoids the vast resources driven into the military, nukes and the space programme but if Zhdanov is succeeded by Kosygin, there could be a lot more cash flowing around to sustain it.