My personal belief is that a contradiction between the professed ideology of a governing party and their actual ideology cannot last for very long. If the membership of the Party are Communist and can articulate Communist ideology, it's a Communist Party and if they're the party in charge, it's a Socialist state. The idea that entire parties (of a relevant size) can exist whose members don't actually believe what they say they believe is Liberalism.

Many Socialists and Communists have ideologies that are revisionist or ineffective but this doesn't make them not Socialists, it makes them revisionist, ineffective Socialists. Their stated aims should be analyzed according to Marxist dialectics to determine if any given group is still truly Marxist, and there will always be some wiggle room with this.

Personally, I believe that the MPLA is still a Marxist-Leninist party, it's just a mildly corrupt one. There is a difference between it and just any other "Social People's Democratic" party in some post-colonial African state. The reason Angola is not typically counted among the "ML States" is because it is not a single-party state; they hold elections where other Parties can and do participate and could hypothetically win.