What if we refuse to repeat this mistake of the Ancients: They hadsteam power w/o using it!

I'm cross-posting this from soc.history.science, where I originally
posted it. It has to do with technology in general, but is also
heavily related to space.

There are a number of examples of ancient peoples having a potentially
practical technology or knowledge in hand, yet who did nothing
practical with it. One famous example is the Chinese and gunpowder.
Another is the ancient Greeks and steam power.

This post is not about steam power ONLY, but I'll go with that
example. (In fact, this post isn't about the ANCIENTS, only! It's
about US not repeating the mistake of ignoring something useful that
is in hand or known about, and refusing to develop it.) I know
Archimedes boiled water in a closed vessel with two open holes,
suspended on a rod above a fire, which would turn on its axis. I also
heard that the ancient Greeks could open the doors of the temple of
the goddess Diana with steam power, however slowly. They would run
this device to impress foreign visitors with the belief that the
goddess liked their offerings.

Now, what if they had thought this through, and developed at least
steam-powered ships back in those times!? Can you imagine if ancient
naval campaigns were fought with steam ships? How much more advanced
might all kinds of technology be today if the ancients had decided to
pursue the R&D of knowledge and technology which they actually had!
There are many other examples, including use of a light beam as
information carrier as far back as something like 1870.

Well, I'm wondering what kind of stuff like that could be happening
NOW? Maybe we are missing no avenue of approach to technological
advance these days. But what if, theoretically, centuries or millenia
distant, they could look back at us and wonder why we didn't develop
such-and-such?

What things might we be putting too little R&D into, relative to their
promise? Antimatter propulsion for spacecraft, maybe? Massively
parallel AI machines, a la HAL 9000, maybe? Geothermal? What? Are you
sure we aren't missing a thing?

I understand NASA has an office for dealing with this concern. Do
other agencies, companies, industries, and even individuals do enough
contemplating of this?