Comment by larodi

Have you tried loading 500k features into QGIS? Well, try it and we talk again.

Govs used QGIS as alternative to pricey ESRI subscriptions, but come to realize that it is struggling even as a viewer. Happily latest versions allow simplification of features on the server side, but these are very new QGISs

also take a look here

https://github.com/qgis/QGIS/issues?q=is%3Aissue%20state%3Ao...