1. No e2e encryption by default (valid, obvious)
2. Telegram has access to the metadata and contacts (valid, obvious)
3. They refuse to deplatform certain content (???)
4. An old and well understood bug/tradeoff/feature which has been fixed or mitigated long ago, after it was reported or abused
5. They didn't respond to Vice, so they "aren't forthcoming with journalists" (what does it have to do with security?)
I'm not using it and no fan of it, but I expected actual technical reasons instead of reading a hit piece with no content.