Congressman says hack of his Signal account proves app is unsecure. Is it true?

Hackers posed as a close acquaintance to take over his account. Of course it's not secure against human errors.

Signal technology is as good as it gets among apps you can install into iPhone/Android, but social engineering can get over that. By a Cryptophone or Bittium for you and your connections if you want to get better security.

Anything can be made trivially insecure if you don’t practise proper opsec.