Let's be honest, Signal is not perfect either:

• It requires your phone number
• It has had some suspicious funding sources
  (UPD: It was funded by CIA)
  (UPD2: Here I will quote www.securemessagingapps.com:

This matters because “money talks”, as the saying goes. If the company or person behind the money is likely to have reason not to protect customers’ privacy, it’s important to know. This could be indicative of the company not doing as they say (Google, Whatsapp, for example) or changing their mind once they’ve onboarded enough customers from whom they can make money.

• It has incidents (at least once) when backend code hasn't been updated for almost a half year or so
  ((UPD)Source: https://www.androidpolice.com/2021/04/06/it-looks-like-signal-isnt-as-open-source-as-you-thought-it-was-anymore/#update-2021-04-06-1-39pm-pdt-by-ryne-hager)

~~(I'm gonna find sources for the last two statements a bit later to not be unsubstantiated)~~
Done.

Although, we all can agree, that Signal is still better than Telegram, or WhatsApp, or Threema, or whatever.
Still, we probably want to look at the better alternatives, like Simplex or Session.