It is amazing how people fail to understand:
a.) the relative scarcity of fresh water and;
b.) the immense difficulty in putting it where it needs to be
Can we handle more people? Yes, but population growth is exponential and I'd rather us focus on sustainability than perpetual growth (which can't happen anyway, there will be an end). Can we handle a lot more people? No. And certainly not quickly. We can't even keep up with the infrastructure needs of 300 million. Let alone, trying to build not only more for those areas, but start expanding out into areas that aren't heavily populated now, because they lack the nearby resources to do so.
We need to replace people with robots and lawyers with nothing. That is the future.