In ArcMap, under the Selection menu, you can choose interactive selection methods such as Add to Current Selection, Remove from Current Selection, and Select from Current Selection. While ArcGIS Pro does allow you to hit Ctrl and click to remove from selection, it is more foolproof to select "Remove from Current Selection" and simply left click on the map. Some of our users have huge selections of parcels that they spend days working on and it would be very risky to have to hit Ctrl first and then click on the map. Also, if you have a very complicated selection, it's nice to be able to Select from Current Selection. It would be great if Pro could have these options incorporated.