The way I see it, is that a guest who has found you on Airbnb needs to book via Airbnb. It is like a spotter's fee. Diverting them elsewhere to avoid the fee is a really bad idea!
Some hosts are listed with more than one platform, and whoever finds the bookings for you needs to get the fee. If we all stopped paying Airbnb for their services it would stop existing, and where would you be then?
How accommodation used to work in the dark ages was that we placed an ad in a classified section in the newspapers or specialist magazines and hoped. Visitor information centres, physical booking agencies. That all cost money too, quite a lot for some of them, impossible for a small operator.