The latest versions of Logic load plug-ins very very slowly. It looks like it now loads AUv3 plug-ins natively asynchronously on the Apple Silicon ARM version, and uses some kind of wrapper for AUv2 plug-ins, which makes them load a lot slower. You can see that when you open an AUv2 plug-in, it first opens in a small size, and then takes its final size. AUv3 plug-ins, on the other hand, open instantly.