In this release, the performance of the Visual Studio extension has significantly improved. We have performed a complete review of our VSX code against modern performance best practices and removed all code that was initially written for VS 2015 and older.
If you have installed PostSharp Tools for Visual Studio, you may have to download the new release and give it another try.
For more details, please read the 6.9 RC announcement.
P.S. If you run into any issues, do let us know via support forum.