TTS is so subjective, a voice that is completely intolerable for one person is the next person's favourite voice ever.

Personally, I absolutely loathe the default Google TTS voice. But what's great about the Play Store is they offer a period where you can try out paid apps and get a refund if you're unsatisfied. So just try a number of voices until you land on the one you like.

You can install other voices. They are paid, but generally cheap. I suggest trying out Vocalizer Expressive. It has a lot of voices for different languages. Each voice is around $4 or so.

There is no "Talkback voice". Talkback just uses whichever text to speech (TTS) engine you have selected. By default that is Google TTS on most phones, Samsung has their own engine, and some others might as well.

I've actually found Google TTS to be quite pleasant, or at least certain voices. Go into your text to speech settings and try out the various voices available. You'll probably find something less painful.

And if that doesn't work and you require more human-sounding voices, there are some engines you can buy, such as Vocaliser, Acapela, Ivona, etc. Just note that although they sound nice, mroe human-like voices can be more laggy and do not adapt well to higher speeds. Most blind people have their TTS set to a pretty high rate to keep up with the speed at which you sighted folks can read, hence why we actually prefer more robotic voices.

Lol my husbof is both blind and autistic and he uses a tts called Eloquence. Recently there was an update for Talkback and it made that Eloquence synth poop the bed. I had to listen to my husband have daily meltdowns for a week until he found out that the Eloquence thing still works on Android if you buy it. He is a strange man that hates the google tts with a burning passion.

I don't really rate them on how human they sound. I rate them on how fast you can have them to and still be able to understand them, which isn't the same thing.

Also guys, have you noticed the voice quality changing when you loggin using a chrome book or something? I don't know what is relation of using a chromebook with android phone, but when I logged in to a chrome book using my google account, the voice quality on my Android phone, using Google TTS, it changed. I find this behaviour very strange.

To be clear, I was using English UK Female voice. After logging in to chrome book, after a while, the voice was same, but the quality was significantly different. Almost sounded like how Google Assistant would sound if you set it's language to English UK.

This happened when I was trying Chrome OS Flex on my laptops.

You have to just stick with it and get use to it. When you get in to screen reading it can be interesting.