> and I haven’t found anything lacking in the latter, UX wise

I'm sorry if I'll sound condescending, but you probably don't use either frequently enough. With telegram it's the little (and sometimes not so little) things, e.g.:

  - voice message transcription
  - you can select part of the message via long-press and use it as a quote when responding
  - massively more complex formatting possible
  - bots as the first class citizens not gated behind some bullshit 'Business' KYC/subscription
  - is not crippled by prohibiting system-level phonebook access like whatsapp
  - extreme flexibility in managing large groups, mostly due to the bot point above
  - and many more

All of the above does not excuse lack of e2e by default, this is almost embarrassing in 2026 now, but Telegram is the most polished IM experience of all the apps I have tried.