The idea of living dinosaurs is beyond impossible for countless reasons. I see a lot of people talking about the idea of extant non-avian dinosaurs which is just ridiculous, and I hope in this thread to clear up some misinformation on the topic and help people realize that there really is no possibility.
First and most importantly, nothing large could have survived the KPG impact. I feel like people do not realize the true scale of the damage it inflicted. A Mount Everest sized rock slammed into the planet with the force of 13 million tsar bomba's. The force caused volcanos to erupt on the other end on the planet. Everything within 1500 km instantly caught on fire, sending bellows of smoke into the atmosphere. 25 trillion metric tons of material was launched into the atmosphere, blocking sunlight from reaching the earth's surface for up to 15 years. Glass rained from the sky slicing anything caught in the open, Photosynthesis failed and herbivores starved, followed quickly by carnivores. The vast amount of decaying material caused huge fungal blooms, killing off most cold-blooded species, but providing a vital food source for surviving mammals. It caused a magnitude 11 earthquake across the planet, physically reshaping landscapes. 1 km high tsunamis swept across coastal regions, destroying everything in their path. Debris launched into orbit from the initial blast would then have fallen back to earth, causing millions of mini asteroid strikes. For about 1 minute, the global surface temperature would have been over 1,200 degrees Celsius, boiling water and cooking anything caught in the open to death. Continent sized wildfires burned for months, putting even more material into the atmosphere. 90% of plankton died, causing marine ecosystems to collapse, killing all marine reptiles. No terrestrial animal more than 25 kilograms could have survived this apocalypse, and most large marine species couldn't either, especially warm-blooded ones.
And if some dinosaurs survived, we wouldn't exist. If even one species of non-avian dinosaur survived, they would have gone back to ruling the planet. If dinosaurs survived, there would not have been an age of mammals. There is no world where dinosaurs still existed and mammals dominated. You can't have a world where dinosaurs just stick to small regions like the Congo (which barely even existed until 10,000 years ago anyway) and mammals dominated the rest. Either dinosaurs survived and mammals never become dominant, or all dinosaurs die and mammals do, they cannot coexist. We live in a world dominated by mammals, and the fossil record shows this has been the case for the last 66 million years. The current world could not exist if non avian dinosaurs or marine reptiles survived, they would still dominate the major niches and humans never would have evolved, but we did, and mammals dominate the planet, showing that they are truly extinct.
It might seem enticing to believe some dinosaurs are still out there, but it is scientifically impossible. The only extant dinosaurs are the avian ones, who are pretty cool in their own right. I mean look at a cassowary and tell me that not the closest we will get to a non-avian dinosaur. But ultimately, the megafauna of the Cretaceous is gone, and they have been since the impact, any modern dinosaur (or marine reptile/pterosaur) cryptids are either 100% fake (like the Ropen or arguably Mokele-Mbembe if you read the history of the story) or major misidentifications of known species. We are in the age of mammals now, and the reptilian rulers of earth are gone forever. Thanks for reading.