You have good news You're a high enough earner to get hit by AMT.
Also, software is pretty good. I used it for years. AMT calculations are complicated. It's effectively a "Flat Tax". "Normal" tax has lots of special interest deductions (itemized deductions, etc), that get you below the AMT flat tax.
Most people should not need tax help. You sound like one of them. Many do not have confidence. Many dan't add. Some are too lazy to do it themselves. Some dedicate their time to job, or family, and just subcontract it to a preparer.
And there are huge differences in competence of preparers.