I was wondering why Marxism was still a thing
Capitalism is still a thing, and continues to hurt people. Marx had insightful critiques of Capitalism.
this placed seemed to be filled with Marxists. So, why?
The site was built by communists
Do today’s Marxists think that USSR did something wrong?
Most do, but some are insane and will defend literally anything in the name of communism.
I would really have to try hard to find a community that would admire Hitler but apparently admiring Stalin, another mass murder seems to be perfectly fine!
Yes, it is abhorrent, but in reality there are plenty of people who admire Hitler too. You might just not be familiar with those communities.
To answer your question broadly, Marxism is mainly a critique of capitalism, and Marx wrote very little about the specifics of how its replacement should function. So I don’t think it is reasonable to blame the horrors of Stalin on Marxism. Marx was pro-democracy and pro-freedom, not pro-totalitarianism.
A more accurate term for what you are describing might be Marxism-Leninism, which was the ideology of the USSR. People abbreviate it to ML.
Someday I would like to see a website with an oval, rather than a rectangular web design. No particular practical reason I can think of other than it would be really cool. The html/css would be difficult, might have to use svgs.