Despite its imperfections, which in my cursory understanding are largely academic, Telegram is an amazing messenger.
It's very quick, feature-rich, and developer-friendly.
Perhaps best of all, it's a nonprofit. So I can expect, with a high degree of confidence, that the organization won't abruptly switch course one day to appease investors.
Telegram has solved the communications problem for me mostly. Before telegram, I had, all of the legacy messenger services (AIM, ICQ, Yahoo, Skype, etc), plus Slack, IRC and whatever I used at work - now I have Telegram, and no longer sign into those legacy services anymore.
What makes telegram a winner for me is that the desktop is a first class citizen, I'm in front of a computer like 18 hours a day - I don't want to have to stop what I'm going and respond on my phone. Yes, perhaps Signal is more secure, and I may try it someday.. but for now.. Telegram has largely solved my 'communications' problem.
Discord has done that for me, but only because all my friend groups are willing to use it. If you just want a messenger that works well, there are a number of good options - that unfortunately don't talk to each other.
A non-profit simply means that it cannot hold money from one year to the next. To achieve that, a "non-profit" could give millions as executive compensation or contract inefficiently to for-profit "partners" who collect the gains. Not saying Telegram is doing that, but the structure shouldn't be adding to a vote of confidence in any way.
It's very quick, feature-rich, and developer-friendly.
Perhaps best of all, it's a nonprofit. So I can expect, with a high degree of confidence, that the organization won't abruptly switch course one day to appease investors.