If the problem is even a problem. 7+ billion people don't just exist. A whole host of factors and variables had to come together to make that happen.
The main issue would be our problem solving brain. Except we don't really solve problems, probably because we can't actually do that, since changing any one thing changes the relationship of everything, so we end up going in a circle. We tried to solve the problem of people dying for various reasons. As a result of the many attempts to solve death, we have 7+ billion people on the planet, and all need fair and equal access to resources, and options in how to get them. That increases our need to externalize the costs of human progress, as we couldn't progress if we had to pay those costs ourselves. One example would be we'll experiment on mice for human progress, instead of the far more rational and fair way of doing it, which would be experimenting on humans for human progress. That opens up at least one can of worms though, and we can't deal with those sorts of choices, because we're not good at figuring out who gets to tell who what they can or cannot do.
Then you get into the questions of whether of not overpopulation is a problem. The planet doesn't care if we're not sustainable, so overpopulation is a human created problem, just like, say, illiteracy. If there are too many of X species, at some point some of them will die because of it, and then life will go on. Human beings don't let that happen, because we have this human created idea of fairness. We've gotten good at not letting that happen. So good, that we have 7+ billion people on the planet, and counting.