As it stands, it’s not E2E by default and it’s E2E scheme is homegrown- which is usually not recommended (though IMO was not a dealbreaker), the big issue there was that there were flaws in the original design of the encryption scheme which makes it harder to look passed the fact it’s homegrown.
Telegram can intercept most messages on the platform, however, ultimately I trust them more than Facebook; so I’m less concerned.
Additionally, since Facebook controls _both_ ends of whatsapp _and_ does not support third party programs, then even though WhatsApp is E2E there’s little preventing Facebook from pushing an update to your phone which backs up all your chats to their cloud.