Lower birth rate is one way to reduce population growth, but the human population needs to be smaller - much much much smaller. And birth rates are only deceasing in rich well educated nations. Unless that wealth and education is spread more evenly it isn’t going to have much impact.
Not to mention the current popularity of humans who are horrified at falling birth rates and clearly prefer war as a solution.
Food is not the problem (until climate change kicks in harder). At least not on a global scale, it’s obviously an huge problem locally, since humans aren’t very good at sharing. Energy consumption is the issue. The Earth receives a fixed amount of energy from the Sun. Humans use energy for a lot more than just food.
True, the Earth does receive a fixed amount of energy. A fixed amount that we are currently using a tiny, tiny fraction of the total of. Even at the simplest measure, the best solar cells in the world, in laboratory conditions, still only convert about 25% of the sun's energy to electricity. We've been developing solar power for what, less than 200 years. It's still a very nascent technology that hasn't even begun to hit it's stride yet.
IOW, while yes, we need to fix things and I'm FAR from saying that we shouldn't. Please don't think that I'm sort of climate change denier or anything like that. I understand that there are very serious issues that require attention. Obviously. But, the point is, these issues are slowly getting attention. Things are getting better. Heck, you talk about war as a solution. We haven't had a large scale war in going on a century. For the first time in centuries I might add. We've had as close to world peace as we've ever had for the past fifty, sixty years.
Again, by every possible metric, things are better today than they were in the past. We're healthier, live longer, live better, we're more educated, less violent, less exploitative, far more morally engaged than we ever have been. Does that mean that things are all peaches and cream? Of course not. Being better than we were a hundred years ago, let alone a thousand years ago, is a very, very low bar. But, it is getting better.
And I find the SF trope of "humanity is a disease that must be cured" which is pretty prevalent in Wellsian style SF to be rather tiresome because it's simply not true.