For some context, wikipedia has a good table and diagram of codecs that do well at low bitrates, many of which are very old (G.722 from the late 1988, Speex from 2003, Opus from 2012 for a few examples)

https://en.wikipedia.org/wiki/Comparison_of_audio_coding_for...

https://en.wikipedia.org/wiki/Opus_(audio_format)#Quality_co...