The ocean level shouldn't be anything. It just is. Come to terms with the fact that nature isn't right or wrong. It just is.
We've all been bred with this mentality that people aren't part of nature and that our mistakes originate in us.
If we "destroy" the environment or the "balance" of the ecosystem or biosphere it was inevitable. If we preserve it that was inevitable. You're worried. I'm not. We all pull our side of the tug a war rope and someone wins and that's the reality and that's the only way it could have been.
Sundaland should be above water. Sahul should be above water. Britain should be a peninsula. All kinds of crap. But the thing is, they're not, so it doesn't matter. We weren't around then. We didn't melt the ice caps, but they melted. It got warmer. Biodiversity went down. People started running things. I figure hot is good for us.
Maybe there will be disease, or famine, or drought. I don't know. But the population will stop growing once we hit a ceiling. When the fossil fuels run out we won't be able to burn them. We'll have to start over from the beginning. The world will cool again and everything will get back to normal.
People die. Animals die. Species go extinct. They evolve. The world adapts to the world.