I think it's the classic case of "when customers tell you something is broken, they are usually right. When customers tell you WHAT is broken, they are usually wrong".
I have an expensive microphone and picked "use original audio" in Zoom, which says that it takes more bandwidth and compute resources for the receivers. Of course, you could just not click that if people complained.
I haven't heard anyone complain. Rather, everyone else also bought expensive microphones and enabled original audio, and the results are excellent.
(Unsolicited tip: some sort of noise gate is really nice so that when you unmute, it doesn't raise the noise floor for the call. I ended up using Krisp, which seems to work quite well. Yeah, it's a subscription service for something your audio interface could theoretically do, and they market it as AI but it's not really AI and that's kind of scummy, but it doesn't take up any space on my desk, and it's not that expensive, so whatever. Sometimes it works too well -- people will apologize for their dog barking, or a fire truck driving by, and it's just met with confusion because that all got filtered out.)
I didn't tell them, "I'm about to switch to the microphone", I switched to the microphone and they told me to stop and they claimed it was using all their bandwidth and to go back to using the phone instead of the microphone.
I'll take the downvotes, that's fine, but how did the people complaining know I had switched to the microphone and what were they complaining about?