Even if climate change gets way worse and we contaminate our environment way more then we do now and additionally to all that have some additional nuclear escalations: It still would be WAY easier for humanity to continue to survive on earth then it is to do so on mars.

Putting up a few human on a mini base on Mars, that's the _easy_ part. Even keeping that base alive for a few years is very easy compared to making the mars a viable/relevant option for humans future survival, and AFIKT that is still years, maybe decades away.