First, the three-eyed dino shrimp are not the Friday Nite Frite. They are real. Some were recently found, dormant perhaps for decades in eggs, swimming in a temporary Arizona lake, created by rainfall. They go back 350 million years to the Devonian period:
After hatching, Triops can grow up to 1.5 inches (4 centimeters) long, with a shield-like carapace that looks like a miniature helmet, according to Central Michigan University. Their eyes make them look angry and wise at the same time — they have two large, black-rimmed compound eyes (like those of a dragonfly or bee) and a small ocellus, or simple eye, between them. Ocellus eyes are common among arthropods (a group that includes insects, crustaceans and arachnids), which are filled with simple photoreceptors that help these creatures detect light, according to the Amateur Entomologists’ Society.
Laura Geggel, “Hundreds of three-eyed ‘dinosaur shrimp’ emerge after Arizona monsoon” at LiveScience (October 6, 2021)
But now, about them not being “living fossils despite those hundreds of millions of years?:
However, Triops aren’t exactly the same as their ancestors, so they wouldn’t be considered “living fossils.”
“I don’t like the term ‘living fossil’ because it causes a misunderstanding with the public that they haven’t changed at all,” [lead interpretation ranger Lauren] Carter said. “But they have changed, they have evolved. It’s just that the outward appearance of them is very similar to what they were millions of years ago.”
Laura Geggel, “Hundreds of three-eyed ‘dinosaur shrimp’ emerge after Arizona monsoon” at LiveScience (October 6, 2021)
What? It doesn’t appear that very much has changed at all. Or if it has, we don’t hear what.
Presumably, the discomfort with the “living fossil” tag for a 350 million-year-old type of life form is that the Darwinian claim is that nature is
daily and hourly scrutinizing, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, wherever and whenever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life.
Apparently, sometimes not.
See also: Stasis: Life goes on but evolution does not happen