That's why virtually every RF frontend oversamples sufficiently to do the sharp filtering in DSP.
3rd ord IMD for non-EE could be described as low power mixers like mixing low power signals and usually the low power signal comes from your intentionally designed radio oscillator, but, whack it with enough incoming RF power and it will go non-linear as its designed to do and start mixing with that incoming signal, mostly making massive levels of interference. You can always improve 3rd order IMD by simply running the oscillator and mixer at higher power levels (which all turns to heat), usually not the best strategy for battery powered gear.