If you are pitting normal humans against enhanced humans you quickly get to the point where you want the demi-humans to be exactly equal in terms of intelligence, tool-usage, social pecking orders, etc. but with higher stamina, natural weapons, ...
In such a case it's unreasonable for normal humans to thrive and all demi-humans not to thrive.
You would simply have to say that humans have survived against all odds - because the odds are not in their favour.
You have to find a typical workaround by giving your humans something that your demi-humans do not have or need.
Humans reproduce faster
It's quite normal to say that there are more humans simply because they reproduce more often, have more children, shorter gestation periods or the timeframe in which women can have children is longer than in demi-humans. In this case the numbers are in our favour.
Humans have technology
The hunters are hunters - why would they develop tools? Your Drider can simply kill you and have offspring, no need for special intelligence and tools. But we humans are weak - that's why we need to be clever. Even if the Drider is similar in intelligence it views tools as unnecessary, whereas they are a decision between life and death for a human. This leads to humans being able to keep up with demi-humans.
Demi-humans haven't been around for so long
This is the "crazy bio-engineer" approach where you are simply at the start, whereas most universes depict demi-humans to have always been there. But if they are only there for a few dozen years then there are simply not so many and the humans can keep them in check.
Demi-humans can't harm humans
Vampires can't get into your house unannounced and they can only hunt at night. These simple rules make it easy to survive for the humans, except for the occasional one that doesn't want to listen to the village elders or the little fairy swirling around their head, wanting attention.
Demi-humans like humans
We (well, some of us) are cute pets. Or livestock.