Agree with the sentiments wrt replacing a working piece of software with an enshitified newer version.

If codec is the issue, winamp supports decoder plugins. If your codec is open source (ish) it might not be too difficult to address the problem.

Stability is a possible reason, as I've seen WinAmp (WACUP included) crash a few times on some streamers I watch, so it probably doesn't play too well with OBS