I use messaging apps exclusively with my Android using friends and family. Can't get my Apple using friends and family to use them. iMessage or the highway. Can't take away the one wee thing that feeds their ego. Fuck everybody else right!? Maddening.
Secure from who? The law? Not likely. Some dude in his basement in Russia who really wants to know where I'm meeting my friends after work or what time my dentist appointment is? Big deal.
Honestly, who is actually stupid enough to still be sending sensitive personal information by text? It doesn't matter what app you use to send it; once it's sent, it's inherently unsecure because now someone else has it in their posession with nothing but their personal integrity protecting it.
Signal messages are (verifiably) end to end encrypted. That means no one other than the sender and receiver can read their contents. You don't have to rely on Signal's integrity, since Signal is (verifiably) unable to read the messages' contents.
Imagine saying e2ee messaging apps are spyware while SMS sending plaintext.
No one told you to use Facebook messenger or even WhatsApp, there are privacy friendly options like signal or matrix based apps (Element for example).