Try asking Pacific Islanders that question. Most Pacific islands are only a few meters above sea. Some have already had their fresh water sources, destroyed by rising sea levels. Most of these people are in danger of losing the land beneath their feet & becoming environmental refugees.
Then there is Bangladesh, a low lying country, without any hard rock, where gravel is made by baking clay. It already is losing significant parts of the country to coastal erosion, some of which was farmland.
If you're not concerned about Pacific islanders or Bangladeshis, then how about Europeans? Significant portions of the Netherlands are already below sea level, sustained by a system of dykes and sea walls. Some of theses are in danger of being overwhelmed by rising oceans and the land being lost.
If you're not concerned about Europeans, then how about Americans? Will Americans want to pay for system of sea walls to protect New Orleans? It already has issues trying to build a wall along its border with Mexico, but that's another issue.
Rising sea levels will inundate land with salty sea water and it cause the lose of softer coastal terrain to erosion, such as limestone cliff terrain in Britain.
The other thing that rarely gets mentioned is the affect that lost coastal habitats, such as mangroves, will have on non-human life. As if human life is the only form of life that matters on the planet and that nature is irrelevant. Humans need nature more than nature needs humans. Some of these habitats are critical to the some fish species and other life forms.