The 1080 Ti is still fast considering its age. And the Gtx 1660 Ti was the fastest non-raytracing card by Nvidia after the first RTX cards were launched, about as fast as RTX 2060.
I've been using this benchmark for getting a big picture:
https://www.videocardbenchmark.net/high_end_gpus.html. The rank can be somewhat different to other comparison benchmarks so viewing several is recommendable. This one ranks the A770 just a few points above the 1660 Ti, not 80% faster. The RTX 4060Ti almost doubles the amount of points. Speed as such isn't the only variable used in benchmarks so reading them requires some keen eye. For example if a comparison tells that the VRAM is 200% higher on one card compared to another but the core of the other is 50% faster, which one would run your games better? Add to that things like heat throttling, power consumption, bus speeds (how fast the data is transferred between components) etc. It's exhaustive and to find the optimal one to suit the exact components in your system would require personal testing which for most of us is beyond our budgets.
The old rule of thumb was to double the overall performance level. In this case I'd go for RTX 4060 Ti despite the Intel A770 having a lower price tag and potentially being tuned to run MSFS well - for unnamed reasons I've got a feeling that Microsoft has a closer relationship to Intel compared to other manufacturers. But does that only mean operating systems and processors, I don't know. Another thing I've learned is that different departments of Microsoft don't consult each other too much when coding updates...
Oh and there
is a 16GB version of RTX 4060 Ti.