I started using it about 8-9 years ago at this point, back when the options were FB messenger or whatsapp. Both were trash and limited in comparison.
I only use signal for work but I find the app clunky and unintuitive. Telegram, being a somewhat privacy nightmare, but not connected to a big data broker company, also gives me the ability to search through a decade of messages to find an old joke, a picture shared, etc.
Telegram is simple enough that I can tell my aging gen x parents and apathetic zoomer siblings to install it and there’s nearly zero friction to them logging in and receiving messages. It solved the problem of being added to a new fucked up imessage groupchat every other week as an android user.