Mohenjo Daro, 2500 BC, was a well planned city with plumbing and flush toilets.
I think the unique thing about our current civilization is pretty much down to our energy exploitations, particularly electricity, in all its uses and all it enables; but also oil refinement and gasoline (both of which are also highly dependent on electricity), even natural gas.
Besides that, homo sapiens sapiens; what we are, with our intellectual and memory capacity and language, has been around for at least 40,000 years, and perhaps 150,000 years. Any civilization we have had that did NOT include those energy sources, including the architecture of the Romans, the civilization of the early 1800s, including high mathematics and astronomy, and the physics of Newton, including the Democracy of the French and American revolutions, would be possible. The Vikings had steel as good as our modern steel in 800 AD. They only used it for weapons, as far as we could tell, but there is no reason they couldn't have used it for machines, powered by human or animal labor. The Romans built the Colosseum using sticks and ropes (and pulleys and ingenious wooden machines), the same for their Aqueducts, still mostly standing. All over the world pyramids and vast structures were built. The Mayans understood astronomy better than modern man did until the 1900's; they pinpointed the center of our galaxy and correctly computed to the day the cycle of days between the sun/earth crossing over that center.
For the purposes of fiction, I would not underestimate the ability of a pre-flood (13,000 years ago) civilization to conduct accurate science, build precision machinery powered by human or animal muscle, and to cut and shape stone or wood to their specifications. I would leave out electricity and refined petroleum (but not refined animal fat), or the use of natural gas.
I would not leave out two major power sources in use for centuries before those sources; wind and water. Dams to store water and exploit rivers and dam drainage with water wheels has been around for thousands of years. Wind mills have been around for centuries, with many configurations. Ways to store energy and release it slowly have, too, which is exactly what we do with something like a cuckoo-clock: Converting potential energy by gravity to controlled circular motion does not require any modern energy source to accomplish; the same thing can be done with a windmill pumping tons of water to a high place and then letting it fall to a lower space; or raising a boulder to a height for a controlled fall that pulls on a gear.
I wouldn't hold back much; such a civilization need not be very primitive at all, it could have large farms, buildings, advanced politics and extensive public works, planned cities of stone buildings like Rome, fully fresh water provided door to door with extensive sanitation, schools for the young, huge farms, commerce and trade between cities.
They may not have the ability to survive the flood. It would still have made sense, then as now, to locate your city on the ocean shore for both transportation and their sea food industry, and they may be covered in water today. There are mysterious stone structures under water that suggest that is true.
I would avoid "primitive" characterizations, I would describe a pre-Industrial Revolution civilization; before about 1800 (when Volta first understood enough to build a voltaic pile (battery)). Edison was born in 1847, the first internal combustion engine was 1872, the first electric light in 1879.