The USSR's problem wasn't in how radical (or not) it was but rather because in tried to reform the wrong things.
Like the way the USSR chose to privatize enterprises BEFORE price reforms, so assets were sold to insiders for fictional prices.
Or the way Gorbachev eliminated the power of the Communist party (the only force keeping the USSR united) BEFORE negotiating a new union treaty (that could have provided an alternate basis for the union to continue).
The list goes on.
The fall of the USSR was a result of catastrophic investment choices followed by catastrophic political choices. Being more radical and continuing to chose the wrong things to invest in or the wrong political reforms would only lead to the situation getting worse.
Andropov and Kosygin were fit to help reform the USSR economically speaking
Andropov's anti-corruption campaign could have borne great fruits if it had continued for longer. There was an enormous need to clear out dead wood and bad actors after the Brezhnev years. It was a great shame for the USSR that he died so soon and the anti-corruption campaign ground to a halt due to Gorbachev's need to secure his power. (And this is another area where China was luckier - they also had a major anti-corruption drive before Deng started his major reforms - no point in trying to reform things if the middle management don't have any interest in carrying the reforms through.)
I used to be a big fan of Kosygin, but my recent reading has led me to question how much benefit his reforms could have brought the USSR.
On the good side (potentially) one of his reforms in particular (never fully implemented) basically introduced the concept of "value added" into Soviet management and planning - if that reform had been pushed more, the Soviet Union could have greatly improved the quality of its goods, the resource and labour efficiency of its enterprises, with potentially far-reaching positive effects.
On the bad side (potentially), the general thrust of his reforms was towards a more Hungarian "market communist" way of doing things, and some argue that this would have made things even worse in the long run. The argument being that market communism diverts the surplus of the country into subsidizing consumption by individuals, thus starving investment. It is essentially a half-way house between Stalinism and capitalism with the advantages of neither system. I've not read enough about why market communism failed however, so I've not yet drawn my on conclusion on whether these arguments hold any water.
fasquardon