By higher frequency, do you mean optical frequencies? If that's what you mean, then it's not just a matter of computing power. It's a matter of optical detectors not actually measuring the phase of the incoming photons. If you lose the phase information, you lose the ability to do interferometry.

CCDs just count photons (incoming photons kick electrons into the conduction band, and you count electrons after each exposure). There are more advanced detectors that tell you the energy of the photons, but not their phase. If you can't measure the phase of individual photons, you can combine light from different telescopes directly, and let nature do the correlation for you. That's what optical interferometers do.