In the context of computing/programming the arrow is bend and walk in a brownian manner. See Alan Kay talks about interesting programs of the 60s/70s to see that what you see as progress today is actually an asbtract[1] regression compared to the state of the art (of course state of the art doesn't have to deal with socio economic reality).
[1] : ideas are either lost or diluted into being re-implemented on new platforms, of course with information loss on the way.
Concrete technology was used by Rome but was lost in a case of, "You don't use it, you lose it."
The political/economical climate changed, and there was some combination of a lack of desire/funding for large structures, as well as a lack of easy access to the materials. So with no demand, there was no need to pass the trade on to the younger crowd.
I can think of a few relatively modern American examples:
The move away from nuclear energy after Three Mile Island and Chernobyl back towards fossil fuels is certainly regressive. Along similar lines, you could argue that lighter-than-air mass transit being shunned after the Hindenberg was another regresson. Speaking of mass transit, Los Angeles killing their trolleys in favor of freeways could also be another possible example.
You could also make a category for ideas that were ahead of their time in terms of cost and practicality. See the Concorde vs today's sub-sonic aircraft. Laserdisc vs. magnetic tape VHS. The Space Shuttle vs the Soyuz capsule.
We could also go on a whole 'nother tangent about lost cultures, languages, artforms, and oral histories we can never positively recreate. Can we judge a society that doesn't know their traditions in period language as "inferior" (as you worded it) or otherwise?
I believe that it was more than a thousand years before modern engineers were able to equal the concrete quality of ancient Rome.
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