Far Cry 6: “Unable to start the game” on Windows 10 boot camp

The error message already tells you that the problem is with your GPU or GPU driver not being compatible.

You never mentioned exactly which 2016 MacBook Pro you have, but according to Wikipedia, your GPU can be:

According to Ubisoft, the minimum requirements for Far Cry 6 is: Video Card AMD RX 460 (4 GB) or NVIDIA GeForce GTX 960 (4 GB).

And for Far Cry 5 they are: Video card (2GB VRAM with Shader Model 5.0)

So your card definitely meets the requirements for Far Cry 5, but might not meet the requirements for Far Cry 6.

There's also the problem of drivers. Even if your GPU is theoretically capable of handling Far Cry 6, it is 5 years old by now, exclusive to a very small range of MacBook Pro devices, and running on a completely different OS.

While it's possible for your GPU to still get driver updates, there's no guarantee it will happen for Windows or add support for new games.

Fortunately, your 2016 MacBook Pro supports external GPUs (eGPU), which can also be used in Windows via Boot Camp. According to eGPU.io, you should have no issues using an Nvidia eGPU in Windows.

What’s the best eGPU for Boot Camp is a question we’ve seen a lot. The answer is a sad joke that long-time Mac users understand all too well; get AMD graphics cards for macOS and Nvidia graphics cards for Windows. One AMD eGPU to rule it all in both operating systems is possible but you’d have to work for it. If you decide to go with the green team, stop reading any further and go hot-plug the eGPU to your Mac. More than likely it will work without much trouble. For the red team, get ready to go on an adventure called, error 12. [...]

Disclaimer:

I make no guarantee that buying an eGPU will make Far Cry 6 run. If it doesn't, the cheapest way to play the game (aside from buying a console) would be to buy a Windows desktop PC without dedicated GPU, and move the GPU from the eGPU case to your new desktop.