The cost and emissions on the newer ones is out of hand, but I don’t think you have much of an argument that diesels have been ruined by technology.
I’ve owned a ‘94 GM 6.5, 96 Ford 7.3, 02 Cummins, 07 Dmax, 06 Ford 6.0, 11 Ford 6.7 and currently have a 20 Ford 6.7 and you couldn’t give me one of the previous trucks vs me buying my 2020.
The newer diesels walk all over the old ones, reliability, power, mileage, all of it. The only difference is IF a new one has issues, it is stupid expensive to fix, but for as far as the diesel doing diesel things, the newer ones will school the old ones all day long. Every single one of those trucks outside of the 6.7’s had major repairs by 150k whether it be transmissions, injection pumps, injectors, glow plugs, turbos, oil coolers, etc. Knock on wood with 300k on the 6.7 platforms I’ve done nothing but maintenance, they’ll pull a house down and will get 21mpg empty on the highway and 10 with a 13k 5th wheel.