@Donald28 This doesn't seem like a huge hassle to me- almost all hosts communicate via the Airbnb messaging with guests- it's important to do that so you have a documented trail in case there is a dispute about something.
Also, you are not understanding those texts you are getting- this isn't some recent thing where Airbnb is intercepting a guest's SMS and making you respond via the platform. What you are getting are text alerts that you have a message in your Airbnb inbox. That's why you can't respond to them- they are just alerts. The messages in them will always be truncated.
A guest can still contact you by text directly to your phone number (altho I don't advise encouraging it, unless it's just something benign, like letting you know they'll be late checking in). But those alerts mean that the guests themselves chose to message you via the platform, rather than text directly to your phone number.