What you call a Marxist system is something that Marx said could only work in the most advanced country if it was ready for it, which in that time was Germany. He said such a system would not work elsewhere.
So what form of Marxism failed? Even Lenin, who many Marxists did not consider Marxist, was a Marxist enough to say that Russia would not establish communism. That the Russian self-described Marxists had the chance to take power in Russia and they took it. That Lenin wanted to take power in early 1917 came as a surprise to Stalin, Trotsky, Kamenev etc., in fact Trotsky was not even with Lenin then. It surprised them because it was not a Marxist idea. Then Lenin introduced the New Economic Policy, i.e. capitalism. Then he died.
Marx clearly spelled out what not to do, and some did what he said not to do, then people attribute the failures of those who did what Marx said not to do, to Marx.