>Are you totally not able to comprehend that material gains in human living come at the cost of the extraction of resources from the ecosystem, and that said extraction is literally unsustainable?
You don't seem to be able to understand that reliance on the ecosystem is not a good thing - it's inherently unstable anyway - just because we were fortunate enough up to this point doesn't mean that a big event like a volcano, weather or biological catastrophe can't destroy the ecosystem and us with it.
Sea level only matters if we can't develop underwater construction in 100 years - As I've said it's unlikely that even in 20 years we will be using traditional farming as a food source - let alone in 100 years - just like we advanced from hunter gatherer -> farming - we adopted the environment to us - the next step is already happening.
You seem to be stuck in the mindset that just because we can't deal with something now it will be a problem in 100 years. If we had to deal with this issue in 10-20 years I would be worried (it would still be possible but it would require large scale dedicated effort) in 50-100 years it's practically guaranteed to be solved by standard progress.
People have been screaming about overpopulation exponential growth, etc. since forever[1], and it's yet to show any signs of being reality.
The solution isn't running back to the caves and wishing everything stays as it was if we stop burning stuff and stop having children so we can enjoy the views - it's to take control of environment and reduce dependency on inherently unstable factors.
[1] https://en.wikipedia.org/wiki/Malthusian_catastrophe