I disagree. Wherever humans go on Earth there are a few constants which never vary and are sort of important. Like gravity and y'know a breathable atmosphere, and unless they're very unlucky a means of obtaining water and food.
None of those constants are there as soon as you leave the planet. So if you break down you're stuffed. If you run out of food or water or heating or air, you're stuffed. If your life support fails on Mars you're stuffed. If you get a serious illness which requires specialist treatment you're stuffed. And so on. You can build as much redundancy as you like into a life support system on a hostile planet but all it takes is one fire and you're toast because you can't run outside in your pyjamas.
On earth, if you must go through a winter without provisions, you're stuffed. If your encounter meteorological turbulences without being prepared, you're stuffed. And so on.
Humans survive on earth as well as we do because of our technology - starting from fire, clothing, agriculture, etc. Without it - for example, tell me, how well do you think Las Vegas' citizens would fare?
And we do have the technology to survive in space, as well. Quite safely, too - despite your alarmism.
Any other arguments?