If we look at it like in that way, it has just as much experience of failure.
I really dislike your argument. I think it is idealistic to say that it was the idea, Marxism-Leninism, that led to these successes instead of the material conditions. Just like it isn't that Marxism-Leninism failed in countries because of Marxism-Leninism but because of specific material-conditions.
This is just a sign of extreme intellectual poverty. For starters, going "stalinist" on everybody to make them all crazy. This is already implying that Marxists-Leninists are unable to reason with, and you want to take it to the extreme to make people crazy. Therefore, you admit that the usual stereotypes (tankies, dogmatic, unable to reason with etc. etc.) about MLs is true.
How can we even claim to be un-dogmatic and serious if we do not attack anyone's mistakes, wether that is Stalin's mistakes or those of any other leftist.
We must try to see how it come that mistakes were made, like the paranoia in the late 30s as a result of isolation, and attack the mistakes.
If we do not act mature, if we act like extreme dogmatists, we will never be taken serious by anyone.