I have some WMS services from non-Esri servers (e.g. GeoServer). However, when I added the service URL into ArcGIS Pro (and also ArcMap). The layers cannot be displayed.
But when I add the service into another Desktop GIS software such as QGIS, the layers can be displayed properly. This is because QGIS has the additional WMS Options with check boxes to toggle such as Ignore GetMap/GetTile/GetLegendGraphic URI reported in capabilities'

It would be best for ArcGIS Pro to support this functionality like other Desktop GIS software and tools.