It's worse in the most important aspect for messaging: it is not end-to-end encrypted by default. It wouldn't be crazy to assume some could get access to your messages.

[0] https://www.independent.co.uk/news/world/europe/telegram-rus...

Except message security. Whatsapp is end2end encrypted by default. Telegram does not, they only provide transport security by default.

Besides the obvious downside of not being meaningfully encrypted (even pointing out transport encryption as just "encryption" is borderline deceptive marketing these days, IMO), until recently it also had a very dubious business model.

It now seems to be pivoting towards ad support, but isn't this exactly what people have been trying to get away from Facebook for?

Signal is a better choice because it uses end-to-end encryption by default.