CSS has a cost and if your EFC is above the COA, you won’t get anything. CSS is more difficult and if you often have to upload financial docs. I did it - and spent a few hundred - but mostly for piece of mind as I knew I was getting nothing.
FAFSA is a no brainer and while people get panicked, it’s relatively easy to fill out - you can even download all your stuff into it from your tax returns and I agree - yes, everyone should fill it out. It likely won’t help but at some schools it will (for example, Chicago will waiver your app fee) and others require it even for merit. It won’t hurt, and if you ever wanted a loan, you need it to get one too.
So there’s zero downside to doing it - well i suppose if the FAFSA got hacked it would be downside. But your college or one you applied to will definitely get hacked (thank you CU Boulder…glad we applied :)) So…yep, get it done.