On a side note, think how conservative music world is, if people are still manufacturing and successfully sell guitar designed in 50s. You can probably take a 50s guitar and connect to a modern amp, or take a modern guitar and connect to a 50s amp and it will work.

Compare this, for example, to smartphone chargers or headphones and their compatibility.

Smartphone chargers had legitimate reason to change. Higher power, faster data, and we learned the hard way that micro usb and all the proprietary connectors before it were fundamentally physically flawed.

Audio hasn't changed at all in the last two centuries. An analog audio signal is fundamental physics and there's nothing to gain or change or improve in any meaningful sense. TRS/phono jacks likewise are just so brute force stupid and rugged that there was never a reason to change.

The connectors and interfaces never changed because the underlying signals never changed because there's nothing to change. Digial electronics on the other hand legitimately have gone through real and worthwhile changes, and been radically redefined many times in the last 60 years.

Oh yeah, you can plug a guitar made in the 50's to an amp that was made yesterday and vice versa with zero issues.

Consider: https://en.wikipedia.org/wiki/Stradivarius

> You can probably

No need for "probably". That absolutely works.

why would the connector need to change? nothing has come out that's really better for analog signals

Sometimes engineers find the optimal or near optimal design early on in the life of a technology. Jet airplanes haven’t changed much since the 1960s.