And technolgy does not necessarily mean artifacts.

A sentient species may use selective breeding or even advanced bio-molecular techniques to provide it with artificial life forms to use as tools, food, sensors, transport, weapons, construction materials and power sources. Actually, humans have been doing that (rather crudely) for thousands of years! Maybe other species are much, much better at it.

Or what about cetacean-like creatures so intelligent and capable in their environment they have never bothered with technology. They still could have mathematics, language, poetry, politics, history, philosophy, art...? Their science might be as complex and advanced as ours, just not based on building gadgets. After all, do whales need flint tools, or fire, or pottery, or glass, or woven fabric? And why should they take up agriculture when dumb food, both plant and meat, is so plentiful and easy to harvest? All they really need to do is learn the habits of the species they depend on, and where they are located, and to communicate that knowledge to their fellows and pass it on to their offspring. Even beasts can accomplish that with instinct, with real intelligence it might make domesticated plants and animals, or machines, unnecessary. We haven't evolved the mobility or the strength to do that, we had to cheat---with technology. Its conceivable any highly complex ecosystem, like a rain forest or coral reef, or even a slime mold, might be "intelligent", and we just can't even recognize it because we operate on a totally different time scale and business model..

On my road to Damascus, I have started to come to some conclusions regarding my interest in SETI. Maybe the Fermi Paradox is in place because ET has never developed spacecraft or radio telescopes. On most worlds with sentient species, the inhabitants have learned enough about their environment to exploit it in ways other than technology, say by learning enough about it to adapt to it, even when it changes. Perhaps that happened in the past, but it left no archaeology. Maybe its happening today, we just can't recognize other life forms as sentient who haven't adopted the same techniques we have.

Think about intelligent termites, distributed intelligence in a hive where the individuals are essentially mindless automata, but the community itself is capable of sentience? All they would leave behind is the nest architecture, structures with no permanence whatsoever unless constantly maintained. And the knowledge necessary to construct and maintain those structures is exercised by the entire hive, not the individuals that make it up.

Maybe intelligence is not so rare in the universe. Maybe tool-making is the Great Anomaly. Yes, we are a race of engineers, maybe the only one. It doesn't mean everyone else is. It doesn't even mean anyone else is.