There’s an important difference between competing on features and competing on “x but not x”. Zoom (which is over a decade old) is video conferencing software, it’s not “webex but not webex”. Zoom stands alone, it competes on quality of service. Starting a “Twitter alternative” is not the same as building a short-form social media service (even if it does eventually become a Twitter alternative).

I think you underestimate MS Teams marketshare. If I'm not mistaken, I've read somewhere Zoom is loosing ground with each Q to competitors. But MS dominates now, for sure. Also worth pointing out, almost none of these online conferencing products were "alternatives to X". They all had their own unique propositions. Superior video quality and streaming, collaboration tools etc. Those who build "alternatives" - fail.