I think it's more that the tooling has been commoditised. Historically, professional GIS was very much about Esri's tools (and, to a lesser extent, MapInfo). Your employability was directly linked to your ArcGIS proficiency.

Now, there's a massive ecosystem of open-source GIS: PostGIS is probably the standout, but also QGIS, everything around OSM, GDAL/OGR, and a hundred others. For government work and some parts of academia then Esri still dominates, but there's now much more to "geo".