Robert.
Here is a link to a zip file with the project I used in the video below. It has a project that has a geodatabase in it with two data sets from the Esri Data & Maps for ArcGIS 2017: cities_dtl and states. It also has a CSV that has median rent prices by state and for many cities across the country. The CSV field that joins to either state names or cities names is "Location"
JoinTesting.zip - Box
** At least there is a workaround other than creating a new data layer with the joined data included. The larger problem I run into is that as soon as you join tables changing symbology or even redrawing the map goes from blink of an eye quick to over 60 seconds. If changing symbology it is usually 60 seconds to determine new class breaks, then another 60 before it re-draws -- IF it redraws. With the lack of an Apply button and every single symbology change taking over a minute to do anything it is very hard to keep using Pro.
Here's a video demonstrating: JoinscausemajorslowdowninPro.mov - Box
Both of these were on a Citrix XenApp server with two NVIDIA M60 GRID cards (8Q profile = 16GB vGPU), 8-core XEON & 64GB RAM.
A man's feet should be planted in his country, but his eyes should survey the world. - G. Santayana