A good accessibility statement names a specific standard (such as WCAG 2.2 Level AA), is honest about any known gaps rather than claiming perfect compliance, and gives a real contact method for reporting problems, ideally with a response-time commitment.
Several jurisdictions, including the EU under the Web Accessibility Directive and various U.S. state agencies, require public-sector accessibility statements by law, and even where it isn’t required, publishing one signals genuine commitment and can help demonstrate good faith if a complaint is ever filed.