So I'm just thinking about the ruins for a moment, and I'm thinking of those outside walls.
They're a hexagon, which mathematically lines up with the triangles and other multiples of 3 we keep seeing across the base.
3. 3 Dimensions. What if that's NOT a hexagon, and is actually a 2D representation of a 3D space. If you imagine the intersecting line, does it not suddenly look like a cuboid?
A few lines are also parallel with this, indicating they could be related to certain aspects, or key indicators of direction?
Could this possibly be a starmap to Raxxla? I don't think Raxxla was ever linked to the Thargoids as being theres, just that it was an ancient world with interdimensional portals that the Dark Wheel exploited for multiversal riches and power.
Perhaps this is the race that built Raxxla, and they're showing whoever finds this the way.
Why else would you build walls with supporting structures behind them if they weren't for defenses? What if this is all part of a symbol drawn to space faring races that find it in the future. They leave snippets of their ancient race for those that find them, such as the urn and casket, and they leave data on their civilisation for those that learn their language, but the overall site seems to house no function - its just a very specific shape and form.
And if you were going to build a starmap using the ground that perhaps wouldn't get seen for millions of years, you certainly wouldn't put it on a planet with an atmosphere that would erode and weather the site down in just a few hundred, would you. So this being on non-atmospheric planet, having no visible function, the walls being pointless and having no official entrance and exit. It's perfect.
Addendum: It reminds me of the scene in the Stargate film, where Jackson explains that in order to plot a course you need 6 points (drawn as a cube and the destination being in the centre of the cube), and a 7th point, being the point of origin.
If this map isn't plotting a course, but showing us the destination, then everything we need could be right there, we just need to know how to translate it.