I wonder what they mean by that. There was a recent post on HN where many people said that it's one of the most polished private messengers (and I myself love it too).
As for the connections to Russia, this isn't an issue, since they store all their data encrypted in datacenters around the world, making it near-impossible for the governments to get decrypted data by court orders in all needed countries.
They also again mentioned the misconception that "telegram is not secure by default". See https://telegra.ph/Why-Isnt-Telegram-End-to-End-Encrypted-by...