Even as a complete newbie in cryptography I can see a problem in your reasoning. "Guilty until proven innocent" is the default when judging on a system. "No attack was named" because Telegram uses algorithms combination that was not proven with time. Nobody used them like this before. Why would anyone try to break it if it wasn't used?
As a potential user of Telegram I don't trust it enough to use it. It's more likely that someone with resources (e.g. government) could eventually break your system than it could break another - time-proven - system.