Capacitance is frequency independant, but it's influence is increasing at higher signal frequencies. This is the case, if the cable is not operated as a terminated transmission line. Then it acts as a load capacitance with increasing load currents towards longer cables and higher frequencies.
Dispersion implies signal edges getting smeared with increasing cable length. Square waves get rounded. At a certain point, the high frequency square wave can't be reproduced any more. Strictly spoken, the fundamental frequency will be still recoverable, so the original waveform can be reconstructed. But existing signal receivers are possibly not designed for.
For an unterminated cable, the strongest signal reflections can be expected to travel end-to-end. So at the receiver, we'll see a series of signal "echos" with a distance of double the cable flight time, decreasing due to cable attenuation and imperfect reflection. At low frequencies, the echo series will have vanished between signal edges and can be easily filtered. At high frequencies, echos are superimposing with next signal edges, and time or frequency domain filtering can't be applied.