Well, a couple reasons. I'm not the best person to ask about the success/ failures of historic communist revolutions, though I think the /r/communism debunking anti-communism masterpost has some worthwhile content on the USSR, China, and Cuba (I'm not as familiar with the history of Albania or North Korea and I'm not a huge fan of the DPRK so I can't vouch for those sections). Here's a couple personal reasons why I identify as MLM:
Revolutionary pragmatism- MLM parties generally recognize that there will be anarchist and left-leaning petit bourgeoisie political movements that can still enact progressive change and doesn't shy away from working with these people when it means thing will get done. This is especially true in the Third World, where the proletariat might be a minority.
The Mass Line- MLM's recognize the need for political organization on a national and international level through a structured Political Party, but they don't see the Party as being 'the vanguard', instead the vanguard is the most oppressed sections of the masses and they should be the ones leading the charge for radical unionization, self-defense for oppressed nations, etc. The party is just a tool for the masses to accomplish this. Thus instead of brigading mass movements to become 'more revolutionary' and sign up to join the party, MLM's instead work with the masses where they are at and develop a working relationship between revolutionaries and the formal party membership.
Effective Direct Action- I'd say this comes out of Mass Line organizing, but it basically means MLM's are damn good at what they do. In Canada, we're leading the charge at the massive students strikes in Quebec and Toronto. At last count here was over 300,000 students on strike in Quebec- that's more than the 2012 Maple Spring. We haven't had a strike that large in almost a century.
Recognizes Indigenous Self-Determination- this is important to me as someone organizing in Canada. MLM doesn't just recognize First Nations sovereignty, but identifies them as the most oppressed section of the proletariat and key to the revolution. It also is A-Okay with First Nations spirituality, something very refreshing for me.
Gets Feminism right- I worked with Trots that were extremely anti-feminist in there political stance basically saying "class comes first" which just isolates women's actual struggles for emancipation. Women make up over 2/3rds of the world's poor and experience oppression on the most subjective level. MLM also has become very pro-LGBTQ2S liberation despite Mao's homophobia.
Nuanced views on Stalin/ Real Socialism- MLM takes a pragmatic view of the USSR and Stalin's administration, recognizing his failures while not capitulating to the Liberal Democratic narrative of Stalin being a monster who personally stalked the soviet countryside eating babies and puppies. It also applies a practical critique to historic socialism while defending it from Imperialism.
Effective Internationalism- MLM recognizes there are problems with ever revolutionary movement, but MLM is effectively combatting capitalist-imperialism the world over. the New People's Army of the Philippines controls a huge portion of the country, there are over two million Naxalites in India, and the Maoists in Nepal have practically toppled a centuries-long feudal despotism. We're really good at guerrilla warfare.