If there were great alternatives by the big players, then Zoom would not 'be a thing' and would not have taken off during the pandemic.

Why would teachers etc. be turning to Zoom if Hangouts etc. was at their fingertips and worked well.

We moved to Zoom before the pandemic because Skype (Microsoft) was unreliable to the point of useless whereas Zoom was solid.

People use Zoom because it's better, and there's really no excuse for Hangouts, Skype etc. to be of inferior quality. Those companies have the best Engineers and all the money in the world. It's a lack of product focus.