I don't agree with that at all.
For a start, socialism goes back further than Marx. The defining characteristic of socialism is the abolition of ownership of private property. Socialism, in the Marxian view, was what was going to arise given the inevitable collapse of capitalism. Everywhere this has been tried, it has ended in death and misery.
The creation of a welfare state is not socialism. It's not even close, unless you want to do some post-hoc rebranding.
Leninism and its descendents might, but every country in the developed West -- where the 19th Century socialists criticism of capitalism was focussed, and whose conditions their program was largely designed for -- adopted, between the late 19th and mid-20th centuries, a substantial portion of the socialist program, and its generally not ended in "death and misery", indeed, compared to those same countries experience under the system for which the name "capitalism" was created, its alleviated the "death and misery".
You can't really judge "socialism" by the results of a particular family of efforts to implement it outside of the context for which it was designed, which is exactly what judging socialism by Leninism and its descendants is.