It amuses me how inevitably the discussion for any new first look swings from “OMG SO OPPPP!!!!” to “Worse than Georgia!” in about a day’s time.
This is predictable, yes, especially for any civ which emphasizes an unorthodox playstyle.
As always, it is impossible to say how powerful the new civ is until we get to try it in practice and also get to know what other changes are made to the game. That said, I suspect the Mayan civilization will be an above average civ at worst. The civ and leader abilities are debatable. I think they are good, but they do have both bonuses and maluses, so I can understand why some might think they are not necessarily beneficial.
The unique unit and unique infrastructure, however, I think are definitely very powerful. Starting with the unique unit, it's an improved version of a unit which is already great, both for defence and offence. The Hul'che will do everything an Archer can, but better. The only thing which could sink it is cost, but seing how my first Archers are typically acquired as cheap upgrades for Slingers, and the Mayans do get some extra gold, I would be surprised if this was a problem. I do understand that it doesn't compare favorably to the Pitati Archer, but that is broadly considered to be the best unique unit in the entire game. You can be worse than the Pitati Archer, and stil be very, very good.
As for the Observatory, I feel like I've had the same discussion about the Seowon to which it is being compared. Some criticized it for being capped at "just" +4, while reminiscing about their best Campus placements from previous games. It is true that you can indeed get some amazing adjacencies for regular Campuses, especially with certain civs like the Dutch, but I get the sense that people overestimate what their
average adjacency is. I also think many underestimate the value of just having a half price Campus. I think it is going to be fairly easy to get a minimum adjacency of +3 for your Observatories, with a fair number reaching +4, and some going to +5. That would give it an average adjacency below that of the Seowon, but again, we are comparing it to what is arguably the best unique district in the game.
Of course, power isn't really the most important thing. What I'm most excited about when it comes to the Mayans, is the unique playstyle they incentivize. Second comes the theme and flavor.