There is a species of aliens, called the erubians, who have tech beyond our wildest dreams. They have fuel cells that can give almost infinite energy, replicators that can make pure energy into any materials they want, and teleportation. All of these use technology that we can not currently comprehend. They also have ships that can travel faster than the speed of light. My question is, with all this tech, would there be any good reason for the erubiams to invent anything knew?
Here's where you get a knowledge gap problem - when you don't know enough about a topic it's hard to see how much you don't know.
For example, why exactly do we twist copper cables together? Why is it important for an antenna to have the precise dimensions it does? Why do we build long distance fibre optic cables from two different kinds of cable and switch periodically? How can we modulate a transmission to limit the interference on a receiver from an open-air optical signal arriving multiple times due to reflection effects?
That last one might get you a PhD if you can prove your answer works. As you learn more about a topic you learn to ask questions you wouldn't have even realised existed with a lower level of knowledge.
So too for the Erubians. To us their replicators are pure magic, the stuff of gods. To them, well, they'd sure as heck love to find a design for a stray quark regulator that doesn't have a resonance in the 300THz band that wastes so many extra materials...
It's very gratifying to do/make/achieve something that nobody else has done/made/achieved before and your aliens will seek this gratification, even if their technology is so advanced that they can't increase the limits of what it can do they'll still be coming up with new things to do with it.
There will always be something out of a curious race's reach and there will always be a problem that can be simplified or solved. Technology is simply a means to simplify things:
- Teleportation simplifies long distance travel.
- Perpetual Energy solves the energy crisis
- Perhaps they also invented easy replication to solve hunger issues.
The simple idea is that there will always be something that needs to be solved that advancing technology can achieve. Perhaps the Erubians find something that needs solving or requires simplification?