What you’ve posted indicates Airbnb took the guest’s side at least partly based on past issues that previous guests have had with either the host or the listing. None of us can say whether it’s justified or not, but we know that a lot may hinge on the whim of a random customer service agent who is not even actually an Airbnb employee.
Remember that Airbnb won’t remove a review unless it violates the review policy in their terms of service. If you believe the review does violate the ToS, point out the specific violation when you contact them.
Members of this forum have previously noted that bad reviews for new hosts can lead to a permanent slump stemming mostly from a psychological impact on guests. If you believe that you’ve worked out all the kinks in your hosting and listing, maybe it’s time to figure out how to do a reset and start from scratch again. This is highly dependent on your goals, though, and whether you believe your rating is preventing you from achieving them.
As far as suggesting or expecting Airbnb to change. It’s not gonna happen. They do not, nor will they ever, have customer service personnel that can support all of the potential problems and exceptions from around 6 million listings, which is why you can’t ask them to do anything that takes more than a couple minutes of time. I’m not sure what “promises” they are not keeping, but you need to manage and protect your business in the scope of how they operate; not how you think they operate, but how they actually operate, and you’ll get a better idea of how they actually operate by listening to experienced hosts on forums like this. Don’t mistake this as defending them, because I’m not happy with how they market themselves to hosts, either. However, given that you agree to their terms of service when you start hosting, you have no other choice when you do business with them.
It’s fairly well-known that AirBnB is more guest-centric. AirBnB decided many years ago that was the correct strategy to pursue for growth and if you look at their STR market share, it has worked well for them, so it’s not likely to change. As others have suggested, listing on Booking.com or VRBO might be an alternative, but make sure you understand their terms, too, because they aren’t all rainbows and unicorns, either.
Regarding some of the “tough love” you’ve received on this forum, you might want put your pride and emotions aside and take some of the advice to heart. In pretty much every industry, the most successful experts come across as arrogant assholes, but that doesn’t necessarily make their advice any less valuable. Don’t take it personally, but do make it your motivation.
Good luck!