I'm not sure which era, or which detuning you are talking about, but the 500 cu in (8.2L !!!!) Cadillac engine in the El Dorado made 400 hp when it was introduced in 1970, and 190 hp in 1976, after several rounds of detuning for smog controls, among other reasons.

This chart is enough to make you cry: https://en.wikipedia.org/wiki/Cadillac_V8_engine#500

Anyway, eventually engineers learned how to make engines that are highly efficient and have very low emissions, basically by making the things as complicated as sin.

For a good 10 years or so, all of these goodies they added (like Mass Airflow Sensors, etc) would fail in mysterious ways, and be very expensive to replace.

Now most of that stuff is pretty solid too.

A lot of opinion about car tech is set by stuff that is 10-20 years old, which is both fair and not fair. It's fair, because it's hard to tell how things will wear when they are new. It's not fair, because engineers have already fixed a lot of things that went wrong in the previous generation.

Anyway, Cadillac now has a 3.0L Turbo [0] that makes as much hp as the 8.2 from above.

0. https://en.wikipedia.org/wiki/GM_High_Feature_engine#LGW

Disclaimer, I work for GM, but I'm on on any engine team.