@Stephanie881, as you spoke several times to the host, I would send a message via the airbnb system to her now. Something like
“Thank you for cleaning the bathroom a bit after my complaints. As said in person, i t is not satisfying, if a bathroom shared by five people is not cleaned for two weeks. The situation is now better, but not yet up to usual standards. It may be approbriate that you hire professional help.
I’m prepared to clean up after myself, as others will probably be. However, you need
to add this condition to your house rules to set correct expectations, especially if no cleaning service is normally provided.
Please provide the cleaning supplies to allow your guests to stay in healthy conditions. I stipulate, that in my opinion, this is still not the case.”
After that messge, I would involve airbnb. There is a possibility to do so via your reservation on app or website. They can call the host and propose a solution.
Unsanitary conditions are a reason to cancel, but It’s a bother to move, find a new place, probably at a higher rate for a shorter stay. Cleaning supplies and a reduction of the rent are a better solution, if you are prepared to take over part of Her work.
If you are all on a longterm rent, you are more like roommates than guests. Is the host living in the apartment? If 5e price is lower than for a short stay, I would think that roommates clean the place themselves, more than guests would, but the host needs to provide the means. Thorough cleaning should be provided, but if there are a few cleaning supplies it’s easier for everyone to remove his own mess.
I travelled a lot and bought a lot of rags to wipe hotel bathroom floors dry after a shower or clean a kitchen in a rented flat 😉
In my tiny shared airbnb bathroom hangs a selection of wipes and rags - maybe half of the guest use them, so you have a chance, that at least one other person of the five will clean too.