the dinosaurs never fully vanished - you can buy them as nugets everywhere
... the question is do they remember their ancestors ruled the world
No because nuggets can’t remember. Once they’re drowned in dipping sauce.
the iconias might nowadays be rather dumb sufficience farmers using whatever passes as 'horse an yoge' on their planets and having no idea what kind of weaponry has been dug into their ground millemia ago.
Maybe yes (“For the World Is Hollow and I Have Touched the Sky”), maybe no (“Errand of Mercy”).
Wait why would a collapsing empire in the milky way would invade a neighboring galaxy? They wouldn't have the infrastructure or funds to support such an invasion.
Maybe they pulled an Independence Day and took their entire civilization with them. Because they can.
Umm so far from my understand of the Star Trek universe, Klingons and Romulans are always trying to expand their borders via conflicts. Heck even the Federation is doing a "soft" conquest by gaining allies and admitting them into the federation, thus expanding their borders.
All of those are corporeal beings, perhaps less evolved than others that have been around longer and have naturally or artificially evolved beyond mortal pursuits.
Also, the Klingons and Romulans are baddies doing their baddie things. Vive la différence. Others out there equally or more advanced have chosen not to. The Vissians from ENT’s “Cogenitor” were more advanced than the Vulcans and were benign enough. Same with the Children of Tama (Tamarians) from TNG’s “Darmok” who were as advanced as the Federation. Even other baddies like Zalkonians (also Federation level tech) from TNG’s “Tranfigurations” didn’t seem as interested in imperial expansion as much as internal concerns.
Come to think of it, the same with the Romulans for half a century until “The Neutral Zone,” and the Klingons seemed to let go of “the Old Ways” until tricked by the Dominion in “The Way of the Warrior.”
The Caldonians, the First Federation, others…who knows, maybe the Sheliak. It’s a big diverse galaxy even if some aliens get more press than others. The Orville did a great episode about something similar with…I won’t spoil who, but there are aliens who evolved so far as to let go of concepts like government and even a sense of self while being extremely powerful.
The Federation does not conquer. Expansion is not the same. And it chooses not to let in many who don’t measure up to its rather high standards. Worlds it could easily gobble up and take advantage of.
That said, maybe all of this, this Star Trek, is but modern day Captain Proton, and in the real world if and when we expand into the stars it will be on corporate and NGO ships with little weaponry of any kind. Maybe there are no moral militaries (and their industrial complexes), and war (and building weapons of) will be illegal (save for anti-asteroid tech and the like) as resources are universally agreed upon to be devoted to more lucrative exploration and expansion. Hell, maybe it’ll all be run by AI, and the future will bear little resemblance to anything in Trek at all. …save for a very advanced and prosperous people trying to live their best lives in an extraordinary age.