Where all the sea level dooms day folks go wrong is that they view the earth’s crust as a static, more or less immovable thing. The crust under the oceans is thinner on the whole and it can flex in the face of vast additional downward pressures. Adding trillions of tons of water weight to the system would deflect the ocean bottom downward; which would offset any sea level rise by quite a bit. Granted, that added pressure will cause an uplift in adjacent areas which in turn means an increase to earthquake and volcanic activity in various parts of the planet as a new equilibrium is established.