I don't think anyone is arguing the science. What I think people are arguing is that the notion of commercial pilots being ignorant for flying something with only an EGT...
I'd be very interested to see how many commercial companies are going down this route. I know of only one myself, but happy to be corrected.
it's all fine and good to spend money on your privately owned aircraft, but calculate the price it'd take to upgrade a dozen 200 series cessnas, Barons, Chieftains etc when most operators are already working to very tight margins given the increased costs of regulatory compliance, SIDS, ADSB, ageing aircraft etc.
In a perfect world operators would be buying new aircraft every 5 years. If this were the case the piston engine would probably be close to extinct because everyone would go for the safer and more economical option of operating turbines, but unfortunately this is far from a perfect world.