Compared to what? If your CPA is less than USD100, and people are interacting with your ads, and you don’t care what the competition is doing, then your campaign is not performing well, is just running.
Once you do some market research and find out an average customer acquisition cost in your industry is USD200, then you can say it is performing well.
Once you’ve tried at least another ad variant, landing page variant, or another audience, then you can say your campaign is performing well compared to other campaigns.
It is not about not knowing what your brand stands for, or what’s your ideal customer. It is about learning what’s the best words combination, what are the best videos or photos, or who among your audience is most engaged with your brand.
Test, learn, compare.