Are you sure about those sea level claims? Scandinavia is apparently rising faster than the sea (see the article below). If so, that wouldn't be evidence of sea levels dropping as much as just not keeping pace. As for being past the point of "no return," it seems impossible to know what we might discover before we get wiped out by catastrophic storms, droughts, etc. Ideally we get creative and resourceful.

https://slate.com/technology/2017/08/why-sea-level-is-falling-in-finland-and-sweden.html