Asteroid impact on the scale of the one that wiped out the dinosaurs
You say you want to wipe out all of humanity. Your biggest problem is that to achieve your goal, you have to wipe out all of it. Even if high-tech society collapsed tomorrow, there are numerous "off the grid" groups that would survive and eventually repopulate the world, from hunter-gatherer groups in Africa and the Amazon to survivalist communes in Canada and the northern U.S. The world is a big place, and human beings have gotten everywhere. It doesn't matter if the government has nationalized all land in the U.S., there will still be other countries that have populations of humanity tucked away. Heck, even today there are illegal survivalist communes squatting on government land in the middle of nowhere. Additionally, when the apocalypse hits you're going to have a large number of people try to escape high tech society and flee into the wilderness. Most will die, but the sheer number means that at least a few will survive.
Because of this, if you really want to wipe out humanity, you need something drastic that would kill off even the people living subsistence lifestyles without dependence on big tech. A simple societal change won't do it. You need a mass extinction driver. My recommendation if you really, really want humanity to die is hit the Earth with a rock on the scale of the one that wiped out the dinosaurs.
One thing we know about the K-Pg impact is that nothing larger than a rat survived on land. Even larger mammals and terrestrial tortoises like Didelphodon and Nanhsiungchelys. This suggests that whatever the conditions most impact were, it means even highly-adaptable animals comparable to modern raccoons and tortoises would die in the aftermath. There's no way humans, who require a lot more food, would be able to survive an event that would wipe out highly-adaptable pest species.
The death blow for humanity in such an event would be food. It is thought that in the aftermath of the K-Pg impact, most of the existing vegetation burned down in mass wildfires and new plant life failed to grow for years afterwards because the sun was blotted out. The end result would be the Year Without A Summer times a hundred, which would have been dramatically damaging to human civilization if it lasted more than a year. Estimates for how long it took for new plant life to grow could be as low as a few years to as much as a century.
Humans could not survive an event like that in appreciable numbers. They would eat up all the stored food and then starve to death because they are simply too large to survive on what little natural life remains and no new plant life will grow for years. The only food webs that would be active would be freshwater food webs (both terrestrial and marine ecosystems would be effectively gone), and even a small population of humans would fish those ecosystems so heavily they would quickly run out of food. Theoretically one could rig up a hydroponic system with artificial lights, but that would require energy to power those lights and finding the appropriate fuel would be difficult. Not to mention what is more likely is the few remaining bands of humans killing each other over the few food resources that remains before depleting them to exhaustion and starving.
Even after the impact, post-impact ecosystems will be dominated by ferns, not edible plants. Fern fiddleheads are edible but they are tricky to harvest, and have to be cooked right or you can get sick eating them.
The Earth would still be inhabitable, and if you give it 100,000 years it would return to being green and verdant. The plants would be recognizable, though nothing on land bigger than a squirrel would survive. You would lose almost all large marine and terrestrial animals though, as well as the coral reefs, etc. It would be an eerie ecosystem, one that looks almost modern but just...empty.
You could potentially achieve the same results with nukes. Just have the Earth get nuked enough that it causes a nuclear winter that has the same effects. Humanity has enough nukes to do it.
Alternatively, if you want to abuse a loophole in the rules you've set up, have it so that natural human fertility has been greatly lowered due to pollution, high-stress due to a modern fast-paced lifestyle, etc. Then when whatever disaster hits say that the lowered fertility rates meant that humanity couldn't efficiently repopulate.
If what you want is a "Life After People" world where the Earth is lush and verdant again, and large wild animals like elephants, tigers, etc., have repopulated the world, forget about it. Humanity is so deeply entrenched on Earth and is so good at surviving you would need either a hugely destructive phenomenon to wipe out all of humanity that would also wipe out most standing life, or else something that attacks humans biologically like a highly communicable plague or genetic sterilization (which it's debatable whether that would even work).