Unfortunately, Blender not very good at caustics. In theory, any path tracer can do them, but in practice, the sampling needs to prioritize caustic-generating regions to be even remotely efficient.

There might be add-ons that help, but vanilla Cycles will take orders of magnitude more samples to create a good image when there's caustics involved than when there's not. For that reason, it's still common to fake caustics in Blender using a texture or projection effect.