People must understand that increasing 1.5ºC of yearly average of global temperature is not the same as the increase of 1.5ºC in any particular day in their local city.
It is not only not evenly distributed around the world (this chart, and the monthly ones on https://data.giss.nasa.gov/gistemp/maps/index_v4.html gives a different picture), that is the average could well mean 10+ ºC in their particular area in several given days (this week there was like 40ºC in Poland, and there was over 50ºC in India and Vietnam the previous one) while decrease in others, that is not just how they feel temperature, but also what is affected by it in larger areas (more energy to fuel extreme weather events, including the ones that brings extreme cold), and that the regions with the bigger increase in temperature have also several of the possitive feedback loop factors for increasing the global temperature even more.
You don't need 100ºC to get a lethal temperature, with half of that (it is becoming increasingly common), depending on hidration and humidity, a lot of people will die. And you die in a particular place/day, not in a global yearly average, after you are dead doesn't matter if the next week the temperature is bearable. And the food sources that feed billions of people must survive too. And the complex ecosystem that enables that you, and your food sources survive as it is now, even if you are not aware of how something that just got extinct was essential, should survive too.