Respectfully???....wellRespectfully, I disagree. The engineering required to broadcast the signal is complex, but the signal itself is very straightforward: sufficiently simple to be decoded in a 1950s era radio set without any digital logic.
You're confusing date of technology with complexity of...
the VOR signal is complex to transmit because IT IS complex.
Digital signals today are as about as simple as they could be to encode/decode.
The VOR signal is both an AM and FM signal in one carrier.... 30 Hz Variable, 9960 Hz FM'ing +/- 480 Hz at a 30 Hz rate and 1020 Hz all AM'ing a VHF RF signal.