Hi @mel888,
This has to do with the age of the plugins - they’re old and in some cases no longer properly maintained by their developer. Newer versions of macOS on modern Macs can no longer run these plugins, and it’s up to the developer to release new versions of those plugins that can run on newer versions of macOS.
But not all is lost! Please see this document on the steps you can do to get (some) of these to run.
Cheers,
Erwin