Most accountants are not good at explaining in simple terms what's at stake with any given report, filing, or decision. Like everyone, they tend to suffer from the cures of knowledge.
Accountants can ghost you. It happens all the time.
Even an accountant who communicates well and doesn't disappear can make mistakes, resulting in an audit. If this happens, hopefully they'll help, but resolving it is your own legal responsibility.
Beyond all that, there are the simple risks of wasting money, running out of money, or doing something illegal in your money management. It's good to lean on experts, but these risks are serious enough that you shouldn't completely outsource their mitigation.