Simple AAC (Augmentative and Alternative Communication) is an extremely simple text-to-speech app that uses iOS's built-in voices. Text input is done with the regular keyboard; and the app even works for other languages that aren't English, if you have their voices installed.
What's new (v1.2)
I finally bought a new computer that can develop apps on iOS 17, so I could finally fix the app! It's usable again! Hooray!