Welcome to Android Central! This is relatively frequently mentioned as an advantage that Windows Phone has over Android, and at this time, I'm not aware of a solution that can completely duplicate that feature. I've recently been using Android Auto on a regular basis, though, and I find that Google Assistant's integration into Android Auto is quite good. When I get a text message (or a Hangouts message), there's a prominent notification that appears on the phone, with a big easy-to-tap button to play the message. After Google reads you the message, it asks you if you want to respond. After your response, it will read it back to you and ask if it's correct, and also ask if you want to add to it. I find it works well. If you don't tap the button in time to respond, I think you can also say "Ok Google, show me my last messages," which will prompt Google to read that last message to you and ask if you want to respond.
You do have to maintain a Bluetooth connection with the car stereo, but if you want to drive safely, that's probably a good idea (rather than fiddling with a separate Bluetooth or wired earpiece, or trying to hold the phone with your hands while driving). If you're listening to the car radio or a CD, and your Bluetooth connection is active, I'm not sure if the system will automatically switch to that Bluetooth connection -- it might depend on the car. One possible solution would be to listen to radio using an app (but this would obviously work best if you had an unlimited data plan), or rip your CD collection and upload to your Google Play Music library in the cloud.