I actually looked at the wiki page, skimmed it. Doesnt actually say the word flat anywhere, I even ctrl+f'ed to make sure.

Id be careful with "modern" mainstream takes on things.

For example, according to modern sources, only one greek god had a flying chariot, that he uses to pull the sun across the sky.

Helios, in Greek religion, the sun god, sometimes called a Titan. He drove a chariot daily from east to west across the sky and sailed around the northerly stream of Ocean each night in a huge cup.

Not true though, each god had their own flying chariot, built by Hephaestus.

Each deity possessed a beautiful chariot, which, drawn by horses or other animals of celestial breed, conveyed them rapidly over land and sea according to their pleasure.

https://www.google.ca/books/edition/Greek_Mythology_Systematized/Lm0ZAAAAYAAJ

Now, all I can find about the mayans is they believed that there was a god at the four corners of the earth, which is drawn as flat.

Now, again, the part I find interesting is not that. Even per your wiki link it says.

Maya astronomy was naked-eye astronomy based on the observations of the azimuths of the rising and setting of heavenly bodies.[12] City planning and alignment was often arranged in line with astronomical paths and events.[13] The Maya also believed that the will and actions of gods could be interpreted in the alignment of the planets and stars. [14]

A.k.a. They used sticks in the mud to mark and record shadows everyday, for hundreds, if not a thousand, or thousands of years.

Thats all good and dandy, but you expect me to believe that these people, on their own, were able to extrapolate the data when a precession is measured over 10's of thousands of years.

The Earth wobbles in space like an out-of-balance top. Each full wobble takes about 25,765 years

Even if earth was flat, how were the able to build models better than what we can do with computers and modern mathematics?

The interesting part, where did they get the calendars from? A gift of god of course, along with domestication of animals, plants. As well as music and healing.

https://oldworldgods.com/mayan/how-did-the-mayan-communicate-with-their-gods/

The Mayan calendar played a crucial role in their communication with the gods. Believing it was a gift from their deities, the Mayans used the calendar to track important dates and celestial events.

They believed that aligning themselves with the calendar would facilitate communication and enable them to comprehend the will of the gods.

https://www.popularmechanics.com/science/archaeology/a43645858/how-the-mayan-calendar-works/

While ancient Mayan culture offered various calendar types, the one that baffled scholars the most was this 819-day calendar discovered in glyphic texts. Researchers have long believed this calendar was associated with planetary movements, especially the synodic periods—when a planet appears visually to return to the same location in the sky, as seen from Earth—of key planets. However, each planet moves quite differently and matching up multiple planets into an 819-day span didn’t seem to make sense.

But it does when you look at it over 16,380 days (roughly 45 years), not just 819 days. That’s a total of 20 819-day timelines.

:shrugs: who knows