I don't share your summary of this paper. I would summarize it as follows: for USA and Australia, high-resolution/precision lidar-based maps are available of coastal areas. For other regions of the world it is not the case (or severely limited). However, gaining an insight into the elevation of land is crucial to determine a region's vulnerability to sea-level rise. NASA’s SRTM has almost global coverage of elevation levels, but is known to be too low resolution to be meaningful for this application (esp. in urban areas). A neural network was trained on the USA lidar data to augment the SRTM data (i.e. make the resolution higher). The network was verified on the Australian lidar dataset (and they got a good match; the model was already published elsewhere before [1]). edit: I should add that the point of this paper was to then have the newly-derived elevation maps be exposed to sea-level change. This is where the maps with flooded cities come from.

Now, you can discuss whether these datasets are representative of other areas, whether the methods make sense, whether the assumed sea-level rise is realistic or if the outcomes of this analysis have value with arguments. But you give none.

To address your other points:

> "Even with sharp, immediate cuts to carbon emissions, it could rise another 0.5 m this century." Then later in the paper share this wildly broad range of predictions

The authors don't contradict themselves here. You even quote them: "End-of-century projections diverge more, with typical central estimates ranging from 50–70 cm under representative concentration pathway (RCP) 4.5". The RCP 4.5 pathway involves major cuts to GHG emissions.

> neural network using the highest levels predicted in the most recent models

Their neural network has nothing to do with the sea-level rise prediction. It simply tries to (better) estimate the current land elevation.

> trained on data from areas with climates and landscapes wildly different

Also verified on coastline that is "wildly different" from the USA coastal line.

> produces maps that freak people out

The truth is hard, sometimes

> and fuel political agendas

Any findings to the contrary would equally "fuel political agendas", namely those of climate change deniers. Damned if you do, damned if you don't.

[1] https://www.sciencedirect.com/science/article/abs/pii/S00344...