This is a really common transition with people who get out of the military. Frequently they're leaving their first post-residency practice, which was 3-4 years of generally low acuity practice. Many but not all did some civilian moonlighting while on active duty for skill maintenance and growth. Some are overseas for a while, with very limited practice.
The short answer is they all do fine. They're all doctors who finished a residency. The memory is there. They're safe.
It helps to go to a practice where the other partners care about you and are invested in your success - as opposed to locums work. But even there you'll find other anesthesiologists willing to talk about cases, though they may not be able to physically help out as often.
You can expect them to not be super efficient right out of the gate, but no one is at a new practice.
People who have enough insight and humility to be asking this question of themselves are going to be cautious and conservative, and therefore safe.
If they're re-entering subspecialty work like peds or cardiac, after a long hiatus, maybe that's an issue. Or the old timer who's been doing 4:1 GI chart-signing work for a decade. But B&B anesthesia for "sicker" people - not generally an issue for people coming from less busy practices.
I'll also add that we all have done a number of things for the very first time as attendings out in practice. New blocks, or procedures we've only read about. It can be a little anxiety provoking but we're doctors and the foundation of our training and education is figuring this stuff out based on the knowledge, experience, and judgment we have.
It'll be fine.