They certainly are not. Our new Deere C&F machines are powered with Tier III certified engines, most are HPCR/EUI engines, and some have more advanced features such as electronically controlled variable ratio turbochargers, electronic controlled cooling fans and so forth. It is something to fire up a 50 metric ton excavator and not see even a hint of smoke (and barely hear it running).
I have spoken with some folks in the Power Systems Group and it seems each new application for a particular engine model is a major undertaking, even just doing a repower for an existing application.
Even back in '98-99 some of our dealership's Tier I repower jobs required a factory field engineer to visit the installation and customize the ECU code to provide a proper power curve for the application.
For all Tier II and later engines, each individual engine requires it's own specific controller code. Engines are required to derate if certain conditions are met, and those vary according to their specific task. We need to file government paperwork to modify derate and shutdown parameters on, for instance, emergency generator or floodwater pumping units.
Interesting stuff (at least to me) and sure more complicated than it used to be.
Gale Banks is the go-to hot rod guy for street diesels, BTW.