Why didn't you include the 580 in your comparison? It sticks out since you included the 1060, where you noted the 1660Ti was 34% faster and only 12% more expensive...
Well the 580 is generally faster than the 1060 6GB, and currently Newegg has an 8GB 580 for $169. Even if the normal 580 price is a bit higher, there are several models available for 189. Why ignore this just because the 1060 is wildly overpriced? The 1660Ti wouldn't looks so good of a value vs the 580...even using the 190 RX 580 price, the 1660Ti would be something less than 34% faster for 47% more cost at minimum (using 190 vs 280 pricing).
I dont think this invalidates the 1660Ti as you cant really step up to that performance class for less. The 590 is somewhere in between (also unduly hot and power hungry) and then you have to go to 1070, GTX 2060, Vega 56, and many others to get in that performance class all at much greater cost. But still, it did seem odd to compare flatteringly to 1060 and ignore much less flattering comparison to 580.
IMO the 580 and 570 are stupid good deals, I got an 8GB(!) 570 for 129 after rebate on a good sale recently, at that price I couldn't even get a 4GB 1050Ti. AMD's upmarket cards may not look so great, but they are currently IMO the only choice around the 570-580 price range.