I don't think you can compare a statesman in Imperial Russia with some of the autocrats they were working for/with. The statesman always had to find his way between two opposing forces: the absolute rule of the tsar and the kind of progress they consider important for the future which mostly meant some erosion of the absolute power. So by definition they had an almost impossible task. The autocrat always had the last word and not because he was more genial but because he had all the power and didn't want to lose it.
How could they have a sound power base if the tsar always became suspicious and let them resign. Witte was not the first one that received this "treatment". The "fate" of Michael Speranski looks a lot like that of Witte. They had some things in common. One being that in their youth, they didn't belong to the establishment but got their way to the top by their talent and the support of Alexander I and Alexander III respectively. Both had liberal and forward looking ideas. And both were sacked when the tsar felt things became too hot to handle. (a difference between Witte and Speranski was that W was more a hard working bureaucrat with a global outlook while Speranski was more like a real intellectual in the spirit of the French Revolution). If you don't call men like these who stood almost alone in their struggle a genius then I guess it was impossible to be a genius in Imperial Russia. Do you know any?
The difference with Stalin is that in the twenties after the death of Lenin there was a power gap in the Communist Party. I guess the most ruthless one took all the power. So not comparable with Imperial statesmen.
I think there were actually plenty of geniuses in imperial Russia, it's just that most if not all of them were in literature, music, and art. As one of Russia's many great literary geniuses put it in so many words, Russian literature has traditionally been Russia's only real parliament... But your post did give me some pause, I think you've made an interesting point.
At the same time, it was obviously the very dependency on the ruler's favor of men like Speranskii and Witte that made them incredibly vulnerable to political backlash and isolation. I mean, what you are reciting is the same story, repeated over and over again, of a brilliant political statesman and reformer initially in the tsar's favor, who falls out of favor and ends his life in total obscurity, even ignominy. There was an obvious lesson in all this. You would think that by the early 20th century Stolypin would have learned it?
I do think it is possible, and one actually has to compare Russian politicians across the board, imperial and Soviet, otherwise how are we to draw any overall conclusions about anything in Russian history? Tsarist politicians seem to have been overly, even fatally dependent on the favor of the tsar. By failing to build up their own power bases they failed to maintain power and their reforms often failed to gain any real traction. That's the long and the short of it... Even the less clever American politicians, circumscribed in their powers as they are by the Constitution and massive legislation, never fail to build up a political base of support, entirely independent of the president. It's absolutely necessary if you want to have a long career and make some kind of difference in politics. It's obvious to any student of American Politics 101, which is why I'm surprised it wasn't obvious to such stellar political talents as Speranskii, Witte, and Stolypin, even if or especially since they were living in an autocracy.
By way of contrast, Stalin proved to be entirely independent of Lenin, although he pretended otherwise, after Lenin's first stroke. And Lenin went into conniptions about this, and even left an entire "Testament" on the theme of how rude and crude and unsuited for power Stalin was, and in the end, after Lenin's death, it made... no difference whatsoever, no matter how revered Lenin was (and he was very revered of course). Because Stalin had built a power base, he was the General Secretary, i.e., the chief personnel officer of the entire ruling party, and he had the entire Soviet secretariat filled with his own men, at his beck and call, and in addition, everybody who was anybody in the upper echelons of Soviet power thought he was a stand-up guy, completely reliable, salt-of-the-earth, hard-working and most of all charming as all get out - in short, all that stuff that matters so much in any actual struggle for power.
Stalin would make tons of mistakes, some of them quite major and unforgivable, as ruler of the Soviet Union, but I think his political maneuverings under Lenin prove that he was not taking Speranskii or Witte or Stolypin as his guides, rather, he was looking to role models like Napoleon after the French Revolution.