Having recently completed an extensive comparison (last year) of Zoom, Cisco Webex (the conjoined legacy H323 and Webex tech), Hangouts, Starleaf, Highfive, and Skype - Teams, I can tell you that usability is high on the list.

For feature coverage, Zoom has basically every box checked apart from the turn-key hardware and hardware management that are offered by Cisco, Starleaf and Highfive.
Highfive is probably the dead easiest to use, but only as long as everyone you're calling is using it. It wasn't interoperable with anything ( they were working on H323 inbound call last year ), and that's a bigger downside than most would consider at first, especially when it basically means that the big board room full of people trying to call you is forced to us laptop microphone and a browser experience.

Cisco's hardware is legendary, and as long as you're only calling room to room it's phenomenal, and phenomenally expensive. And since no one is in those conference rooms these days, you're left with the laptop experience, which is abysmal when you can see, and more often than I wanted to admit, it just plain didn't work. I went in to our pilot thinking Cisco would take it, and I was blown away by how bad the remote user experience was or even in the office on great wifi. The app sucked. But the socks are great. Wearing them right now actually.

Zoom's biggest downfall is that they are a SaaS company. Relative to a lot of other things, that's not bad but let me explain. They don't make microphones, they don't make touch interfaces, they don't make speakers and they don't make displays. Now you say, of course, let the folks who are good at that do those things. But in the demonstration Zoom setup you have a who-knows-what Dell or Lenovo or Mac mini, a TV, a webcam, probably an expensive one like a Huddly IQ or a Logitech Meetup, and two iPads. iPads drop off wifi all the time and when they're run all the time they do strange things. Also, if you're at all concerned about the implications of having an iPad on your network, or walking out the door, you've got to have some MDM like Jamf. I can't tell you how many times I have been on a call with someone who supports Zoom and I hear that they just use it as a no-user workstation, flipping to other applications or loading other VC software on the Zoom system to test. So what you say? How good is your network segmentation now? You've got iPads and the zoom machine on the network together, because they have to talk. What else can that computer reach if you exit the application? food for thought.

Hangouts suffers the same "don't make the hardware so it runs on everything" but then it also suffers from the "terrible video experience" and "will Google quit this too?" problems. And it's blasted expensive now that it's only Enterprise. Zoom still has the freemium hooks and they're making hay.

Skype is turning into Teams which may eventually eat everyone's lunch but it isn't there yet. But it's coming.

Starleaf was our incumbent and suffered from the same thing as Cisco, Great conference room experience, but laptop experience was poor. They've made huge strides and I think more folks should know about them.

Zoom just worked and your mom could already use it out of the box. UX wins. You just have to make it secure.

it's like some shared-responsibility model or something. :)