Why do basically all South American leaders now suck?

[I spent the winter writing songs about getting better]

The only one now who's decent at all is Moreno in Ecuador.

[Epaminondas]

It was the same throughout the 90s.

[urutzizu]

Tabare Vazquez is competent. Martín Vizcarra seems like a decent man too.
But yes, Maduro has been very bad for the democratic left in South America. He helped radicalize the right and forced other left-wingers to have to defend themselves against the constant ( and mostly unfounded) accusation that they were sympathizers of Maduro and were going to ruin their country in the same way. The accusations that Alejandro Guillier, hardly a chavista, was going mean "Chilezuela" for Chile is a perfect example.

Just like the "Pink wave" receded, it seems that with Amlo, with Alberto Fernandez, with the unpopularity of many right-wing Presidents, there is slowly, despite Maduro, a resurgence in the Left. It seems, as i hope, that this time it is the more moderate, democratic left, not Authoritarian left-wing populism, that is coming back.

[Skye]

Now?

[kaoras]

Before somebody says Piñera, no, he is a clown who governs according to Twitter hashtags and TT.

[Blue3]

What about the one in Uruguay?

[PSOL]

Morales has been pretty solid, and even with a bit of stagnation going on.

[I spent the winter writing songs about getting better]

What about the one in Uruguay?

All he's done for the most part is fight against legalizing abortion.

[urutzizu]

Morales has been pretty solid, and even with a bit of stagnation going on.

Losing the 2016 Term limits referendum and having the Court, stacked with his Appointees, legalize his indefinite reelection anyway was a really bad move. Also for all the Talk about empowering the Indigenous Nations, he has been very willing to push through road and development through their territory against their will.
He did many good things for Bolivias Poor and Indigenous at the Beginning, but power corrupts, and Morales is an ideal example of this.

[Absentee Voting Ghost of Ruin]

Ask Santander? I believe his namesake's superior had a quote about this...

As you know, I have led for twenty years and have obtained only a few certain results:

    America is ungovernable.
    He who serves a revolution plows the sea.
    The only thing one can do in America is emigrate.
    This country will fall unfailingly into the hands of the unbridled crowd and then pass almost imperceptibly to tyrants of all colors and races.
    Devoured by all crimes and extinguished by ferocity, the Europeans will not deign to conquer us.
    If it were possible for one part of the world to return to primitive chaos, this would be the last period of America.

-Simón Bolívar

[MASHED POTATOES. VOTE!]

The only one now who's decent at all is Moreno in Ecuador.

I have a feeling you're saying this mostly because of Assange. I suspect you're not familiar with his increasingly conservative policies:

https://en.wikipedia.org/wiki/Lenín_Moreno#Internal_politics

What about the one in Uruguay?

All he's done for the most part is fight against legalizing abortion.

While I strongly disapprove of Vazquez's stance on abortion (and his attempts were ultimately unsuccessfully), it's simply inaccurate to say it's "all he's done for the most part". The Broad Front coalition under Vazquez and Mujica succeeded a great deal in cutting poverty and unemployment, among other domestic achievements.