Mesozoic

Triassic is good enough. "Our journey continues in the period denominated the Jurassic. The supercontinent of Pangaea has split into two landmasses - Laurasia and Gondwana. While not as arid as the Triassic, the climate is still hot and humid, with forests extending into the poles. Following a brief extinction event, out of literal ash, the dinosaurs rose like a phoenix, quickly dominating their environment in all shapes and sizes. Long-necked behemoths known as sauropods browsed above clashes between formidable carnivorous theropods and spiked stegosaurian prey. Flying reptiles known as pterosaurs patrolled the skies, and giant marine reptiles had their own dynasty. Their success will grant these species to rule some more million years, in which they will diversify even more." "Our journey ends in the Cretaceous period. Continental drift continues, as our world begins to take on a more familiar shape. The climate is still considerably warm. Dinosaurs remain in power, and have hit their evolutionary peak. Theropods continue their legacy with the largest carnivore to ever walk the Earth - Tyrannosaurus rex. Mighty herbivores known as ceratopsians fight for their survival with all numbers of horns. Some tiny dinosaurs have taken to the air, but live under the shadows of the biggest flying animals to yet exist. However, it was not to last forever. An asteroid the size of Mount Everest strikes near the Gulf of Mexico with the energy of 10 billion Hiroshima bombs. The impact unleashes global wildfires, in turn enveloping the planet in a firestorm. The ensuing 15-year period of freezing darkness would've finished off any survivors above 25 kilograms. Small, unassuming critters known as mammals, which previously lived in fear of the dinosaurs, were given the opportunity of taking their place. While this was the end of the dinosaurs' rule, it wasn't the end of their kind. One lineage of flying dinosaurs survived, rapidly diversifing in spite of the mammals' rise to power. They still exist with us today, where we now call them birds." More on reddit.com

Anumals typically don't eat other animals they're unfamiliar with - that's an oddity unique to humans, and part of why introduced species are so destructive. Predatory dinosaurs most likely wouldn't be that dangerous to humans. In particular the larger predators almost certainly wouldn't be that dangerous. They're interested in hunting hadrosaurs or sauropods, not some weird little bit size fuzzy thing. Would you chase a chicken nugget for a quarter of a mile? Yeah, a tyrannosaur isn't going to waste its time on you either. Y'know what's super dangerous? Herbivores. Hippos kill more people every year than any other african animal, because they're stupid, mean, and won't suffer another animal to live in their line of sight. Elephants in mating season are terrifying. Eats plants=/=nice. They have to be mean: stuff is constantly trying to eat them! Y'know what's even more dangerous? Diseases 150 million years away from the nearest vaccine or antibiotic. All sorts of strange, deadly and totally unknown microorganisms, wothout any medical infrastructure to treat it. Everyone gets sick, terribly sad, bye bye! Let's see, anything else? Plant foods can't be trusted, as there's no way of knowning whats safe for human consumption and whats not. Air composition would also be different. The different gases would almost certainly cause problems of some kind. In short: large predatory dinosaurs are probably the last thing on the earth they need to worry about. More on reddit.com

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And yet, all those smaller animals were abundant across most Mesozoic ecosystems, so there must be flaws with your reasoning. More on reddit.com