Not the original commenter, but I have faced similar friction from people who are not grandmas or quarterbacks. I don't particularly agree with its tone, but I agree with the original commenter's general message.

I won't be so confident to identify what it is, but there is something that causes "end users" to bristle at Zulip.

Where I'm coming from, everyone uses Slack. I spearheaded an effort to switch to Zulip because our Slack server is on a free plan and our messages get sucked into the void after 60 days now. Everyone agrees that this is bad, and that we don't have the money for Slack premium (we're an academic organization, so AFAICT we wouldn't even have to self-host to avoid paying), and yet so many people do not want to switch. Here are some common responses I've gotten:

* I refuse to use another messaging app and Slack is nonnegotiable for some of my collaborators.

* I don't want to learn a new UI.

* I don't want to learn a new UI that isn't basically the same as Slack.

* I will only switch if everyone else switches.

This is half a social problem ("I will only be receptive if everyone is using this"), but I do think there is some legitimate friction in Zulip's UI. I am fairly confident that we could successfully switch to Zulip if the Slack dissenters could be convinced to use Zulip --- or if Zulip could somehow be coerced into being more Slack-like.

As the "agent of change" at my organization, I felt like the resources Zulip provides are lacking in what I really need. Like I know there are technical details on how to move to Slack (https://zulip.com/help/moving-from-slack), but what I really need is help with the above: convincing people to try and acclimate to the UI. And yeah, I kind of agree that a 2 minute video on how to use Zulip is not the resource I need since it presupposes a degree of openness and cooperation that I don't have access to.

These are somewhat disorganized thoughts, but happy to expand upon anything if you're interested. I really do want to successfully move our org to Zulip since I'm tired of our messages disappearing.