DEM data from Sentinel 3?

A bit of a beginner question but is there a way to generate Elevation data from Sentinel 3 (or 1)? I have an AOI covering a 60km*60km area. The area is a relatively flat dry lake bed but for some reason the existing DEMs for the area (I have tried all the freely available ones - SRTM, ACE2, GTED, ASTER etc.) are not very accurate. The ACE2 dataset is the worst with a ±10m error within a couple of pixels when the whole lake bed only varies by 1-2m. I find it confusing (to this beginner) that you can measure sea level within a couple of cm but land surface is highly variable?

Sentinel-3 is not appropriate for DEM. You might get it from Sentinel-1 somehow but it is quite a bit complicated and you would have to use raw SLC data. Some more information here:

Might it be that these old DEMs were done when lake was still covered with water? If so, it would be impossible to generate DEM from satellite imagery.