Which platform are you using?

I'm primarily using apple devices and their TTS is surprisingly good. Not sure if everything related to their tts experience works on-device but at least the voice models need to be downloaded when choosing a voice. The quality of the newer voices are insanely good.

I've been using this feature for multiple years and the moment I started my research to write this blog post I realized that other platforms unfortunately can't offer the same kind of experience and as you said the quality of the voices just can't keep up - it still sounds robotic..