But…that’s what you’re doing? Streaming the game at 180mbps…

No. Map and weather data is being streamed, cached on your SSD and then the game engine loads it from there into RAM and uses it in combination with other locally stored data and locally performed physics calculation to render the game on your machine. You get an uncompressed, high quality image and low-latency input, freshly baked by your graphics card for your eyes only. At 1080p and 60 fps, that's already 2.98 Gbit/s per second generated by your GPU and sent to the screen as is. At 1440p, we are at 5.31 Gbit/s and at 4K, 11.94 Gbit/s. DisplayPort can handle up to 20 Gbit/s per lane and use up to four lanes, by the way.

Xbox Cloud Streaming only uses up to 20 Mbit/s (and that's very optimistic). At the advertised 1080p, this means that only 6.7% as much data as generated on the server is reaching your screen.

The problem with game streaming is that in order to limit latency, they have to compress the image and send it very quickly, 60 times per second, which means they have just 16.7 milliseconds for each frame - and do this for potentially millions of users at the same time. This cannot physically be done at any decent level of quality. It is far easier to send much larger amounts of map data that is not time critical: It doesn't matter if it's even a few seconds late on your machine, since the game engine will render something with the data it already has. At worst, you get some building or terrain pop-in, whereas if even a single of the 60 frames required for direct game streaming is being dropped, you'll immediately notice it as stuttering.

That sounds like a great reason not to buy this game.

If you don't have the hardware to play this game locally, then I would not recommend it. If you have - and a base Xbox Series S is enough for a reasonable experience, which costs just 300 bucks new or about half as much used - then there is no reason for using the streaming service, unless you absolutely have to play it on your phone at work.