At the risk of sounding like a tankie: a huge factor why none succeeded is that the west and capitalism did their best - ranging from economic warfare to the CIA murdering popular leaders in Latin America - to make them fail.
I don't disagree that modern socialism has yet to be achieved, but to claim no socialist systems have ever existed is a very settler-colonialist take. Even Marx himself knew better:
"to look beyond the Middle Ages into the primitive age of every people—and this corresponds to the socialist tendency, though these learned men [Georg Ludwig von Mauer, known for his studies of early German communal society, and Jakob Grimm, the philologist and cultural historian] have no idea they [the “primitive” communal forms] are connected with it [the socialist tendency]. And they are then surprised to find what is newest in what is oldest." source
Nope. It doesn’t matter how well your government is, the rich will get richer and the poor will get poorer. Then the rich will eventually buy the government to even further increase their profits.