hii @crypto.piotr,
When we give very high apy it seems like a double edged sword , 1) We get a lot of new customer ( hight marketing like you mentioned) 2) But we usually gain an customer base thats here only for the profits and once the apy reduces they tend to Stop 🛑... supporting the project because they no longer are getting what they joined the project for.
If we leverage the boon vs bane here , in my perspective I would focus on something that gives utility to the the project and maybe add the apy feature in the future once we have a decent customer/ support .