Instant book is a setting in Airbnb that enables booking without having to request approval from the host. This is mostly done by commercial listing and less done by hosts who invite people to their homes.
Even if you filter out all “Whole house” you will still get a lot of hotel rooms and hostel beds in your search result.
Try adjusting the price range a little bit and also use the map to zoom out of the city center.
Many people live in the suburbs so if you are only looking at listings in the city center chances are high you only find overpriced hotels.
When you have found a booking that seems good to you the last step is to read reviews. You want to read about how much the host interacted with the guests and how the overall atmosphere was between guest and host. That way you can make sure your host wants to talk to and spend time with you when you are their guest.