Most plugins don't use these APIs directly, they rely on wrappers like JUCE. Once JUCE supports CLAP the plugins will follow. That should happen in the next year.

The bigger problem are hosts. While Apple and Avid will probably never support CLAP, everyone but Ableton does. They move slower than the rest of the industry (taking a decade or so to implement VST3). Which is odd because CLAP is significantly easier to use from both the host and plugin side.

That said, you can wrap a clap plugin as a vst3 or AU today. It's probably the lowest friction way to do it to be honest.