I hate to be the bearer of bad news but FRAGSTATS is functionally dead. Kevin has retired and it is no longer being maintained. Neither version tends to work under Windows 10 (but you may get lucky). Kim WIth's lab has taken it over and moved functionality into the
landscapemetrics R package. Among many, one distinct advantage of using R is that there are packages that support the generation of null landscapes. Testing against a null is an essential process in evaluating the significance of your findings.
You can try Patch Analysit (vector plugin for ArcGIS)
but, I am not sure about current version support for later ArcGIS releases or ArcGIS Pro. It fell out of development for some time but, I think that somebody picked it back up, at least up to ArcGIS 10. This is the only option that I am aware of that operates on vector (polygon) data. I would point out that if you are wanting to evaluate change in patch dynamics, the vector model is a horrible choice for your analysis. The raster data model would be much easier (eg.,
y - x) and remove the inherent boundary uncertainty in comparing vector data.
If you would like to stay in the GUI world I would recommend looking at the plugins for QGIS. The LecoS plugin has been around for some time and should be fairly mature. I believe that there is also a plugin called LandMet but know little about it. The GRASS GIS software also has a landscape metrics module.