ANY change can be considered good or bad, depending on the scope of consideration (that is, who is benefiting and who is not) and the time scale involved. There isn't one simple answer.
Example: let's say the ocean levels rise by 10 feet. The current coastline, including many cities, will be inundated. People who own property along the current coastline, which in the US is generally valuable, will lose their land. Will society reimburse them for their loss? Or will they simply be out their investment? That would be bad from their perspective, I would think. On the plus side, there will be new coastlines, and people who currently own usually-less valuable interior land will find increased prices for their now beach-front property: they'll make money...unless the ocean levels continue to rise, in which case other people further inland will then benefit, while those whose land has been covered will be sol. All those people who currently live, and all that infrastructure that is currently above sea level will be swamped--that's a negative, because people will have to move (where will they go to live?), investments will be lost, etc. But new homes will have to be built, new infrastructure created...meaning jobs, and investments, and opportunities to make money...
There will be less land area, but the population will have to live and make a living on what's available, so that will tend to drive demand up, leading to more opportunities...and costs...and so on... Most of the fruits and vegetables consumed in the US are produced in the Central Valley of California, southern Texas, and Florida--all of which will be at least partially inundated by even a 10-foot rise in sea levels--that will have negative impacts on those areas, but maybe the rising sea levels will also open up new areas for growing food, so that might be a positive...
Net, will a sea-level change be a positive or a negative? Until you have a really good and reliable economic modeling computer program, it's all guesses. Do you want to make plans or place bets--gamble your future, of that of your children and grandchildren, one way or the other--on speculation that climate change is, or is not, real, and is, or is not, going to have an impact on society in the future?
I think prudence dictates we do more research and try to find ways to be more efficient, and cause less unintended effects, in the future. That kind of investment will allow us to adapt to whatever changes happen.