That’s definitely not always the case. My CPA made a mistake on my state taxes and they explicitly told me I was liable because it was my tax filing. I suppose they could have been lying to me but I doubt it.

Different level of "liable".

Yes, you are, in the end, responsible for your own taxes the filings. If a mistake was made and you owe additional taxes, you have to pay them as well as any penalties, etc. But if you used a CPA, you have the option to sue to recover any loss they caused you through negligence.