"Poor" is really a woosy adjective.
If you're willing to express the size of the objective mirror in terms of wavelengths instead of
inches or meters or yards, then a radio telescope and an optical telescope with equal diameters
have equal resolving powers.
The familiar difference in their dimensions is simply the obvious consequence of the difference
in the wavelength of the signals they happen to be looking at. The shortest radio waves are
something like 2,000 times as long as the longest light waves.