> by today's standards.
Which? Whatsapp call sound shit. Mobile phone calls sound shit.
I did Mumble to get some acceptable quality.
> Whatsapp call sound shit.
Not for me; it's way better than any landline I've ever used.
Not sure what we're doing differently – are you sure it's not your or the other party's speaker or microphone?
> Mobile phone calls sound shit.
Not for me either, at least not when EVS ("HD voice") is used, which is more often than not these days when calling friends/family.
2G connections used to sound quite bad, but since 4G, the limiting factor for me has been the other side being on a landline (mostly for business calls), which usually doesn't support wideband audio.
On top of that, I think many remember "landline quality" in terms of a relative comparison with potato-quality early mobile phone codecs, analog mobile phones, heavily compressed discounted long-distance calling circuits etc. of the time.
Yes, landlines were better than any of that, but it doesn't mean that they were actually good by today's standards.