Yeah Telegram absolutely nails the desktop experience like few other chat apps do. The way they put all the functional bits into a library to make it easy to build high quality third-party clients helps, too; while the Qt client is quite good across platforms, users also have the option of a Swift-based client on Apple platforms, a WinUI/UWP client on Windows, GTK client for GTK-based Linux desktops, etc which takes it that extra mile. Heck there’s even CLI clients for users of that inclination.

Its security is questionable but it gets users by the boatload anyway because it doesn’t consider any platform an afterthought, they all get first-class treatment. Other cross platform messengers would do well to embrace a similar philosophy.

Sure. Different projects, different goals. At every instant where Telegram had a decision to make between better user experience or user security & privacy, Telegram opted to make a better experience. Signal took significant UX hits to make the privacy promises it makes. The two projects are essentially not comparable. Like, the sane thing to compare Telegram to at this point is Matrix.

Of course, but it’s not just UX that’s being traded off but also potential for mass adoption, and evangelism is likely not enough to close the gap.

Again: different projects, different goals. What Telegram is doing is inherently viral; the platform has an emphasis on bringing huge groups of people together, and the resulting design affordances, and that's a goal that basically works against privacy in the first place. Signal's original goal is to replace intimate messaging.

People who love the Telegram affordances wish that the platform would also suffice for intimate messages. Why have two platforms, two UX's, and (most importantly) two user bases? People who live Signal wish the other thing.

But you can't have both. They are incompatible design spaces. Telegram's security story is atrocious. It's best compared with Slack, not with Signal. If you're looking to compare a serious secure messenger with Telegram, look at Matrix, which has many of the same goals.

It is important that there be a messaging platform in common (if not universal) use that is fit for purpose for secure messaging when it really matters: when the compromise a message could cost lives or fortunes. Most "secure messaging" is LARPing; it doesn't matter if the "E2EE" in a pseudonymous 500-person chat room is secure. By all means, make it harder to dragnet that channel, modernize the protocols, whatever. But you can see right away how little security really matters to these groups, whether they're on Telegram (with no group security) or Matrix (which at least tries), because messaging app affordances are all people talk about with them.