This does not seem likely, the bar for a region being "unable to support humans" is very high. People already live in cities that need to support themselves with food from elsewhere, and worldwide calorie production per capita is increasing.
A huge portion of our farming is currently unsustainable. Yes, we are producing more right now, but this production is on a clock. Even without any change in climate we are screwed. Look at how many places in the world are currently undergoing water system collapse. California, a huge crop producing state, has areas that have sunk nearly 30 meters because of pumping too much water. Those same areas are highly dependant on bringing in water from long distances away. Now add unstable weather patterns the the propensity for longer droughts and tell me what you think will happen?
We are not dealing with a climate change problem. We are dealing with
A long term water supply problem
A soil salinization over vast areas problem
A soil decarbonization problem over vast areas
Increasing temperatures that are pushing our current high yield crops to their limit problem
A globalized transportation system that will quickly spread crop diseases problem
Humanity is playing russian roulette with these issues. We will get a perfect storm one of these years, for example across the midwest US being hit by a drought and crop rust and we could see a near complete failure of our corn harvest. We are talking about the potential loss of 750 million tons of calories that will rock the world to its foundations.
Sounds like a cautionary tale to our current situation.
I feel like the problem with climate change is that by the time the effects get so bad that everyone will be on board to actually put a significant amount of resources into prevention and mitigation, it will be too late to do anything, because there is a time lag between ceasing emissions and the climate stabilizing. Additionally, all the greenhouse gasses you have already emitted are still in the atmosphere so just stopping emissions will only stop the heating up (if we are lucky) and not automatically result in the climate returning to "normal".
I hope this doesn't come across as overly-aggressive, but it seems to me like you don't really understand much about how the Dutch lived below sea levels for centuries.
Yes, over many centuries, they have built all sorts of contraptions in order to gain more land from the sea or lakes. But this is expensive, takes up a vast amount of skill and planning and is only feasible in certain terrain. The Netherlands is also a small and very rich country. To believe that the whole world can do this is complete insanity.
Huge swaths of the globe will experience fatal web bulb temperatures multiple times a year by the end of the century. Very clearly this makes a region "unable to support humans".
Furthermore, a lot of the areas that will suffer from fatal wet bulb temperatures do not have the wealth to provide AC to everyone. This will drive mass migrations of people on a scale we have never seen before, destabilizing neighbouring countries (or more likely, leading to mass murder).
Finally, this is another positive feedback loop: more AC required -> more energy required -> more severe global warning.