This makes me very sad because I fear it's true. I want to play around building successful side projects, but to get traction I need to play around with ads. To buy ads with my own money and knowing 95% of it will be wasted is too much of a blocker.
It's not SAAS, but e-commerce.
Elon Musk has conversations at scale on Twitter, no ads needed.
If you know who would use your product, find them and have conversations. Talking to real people is the first step to great ads anyway.
If you don't want to have conversations with your users, or don't know who they would be, maybe you would be better off building something else.