A project management office is usually looked to to provide a consistent project infrastructure within an organisation. It also connects the organisation's executive to project performance information in a reporting system.
It can, should, indeed, must be more: to build project capability and bring benefits from projects.
My project managers have meetings with our version of a PMO each month, where they dutifully talk about activity completed and delayed, and risks that have emerged. No work is done to connect our projects to any other projects in an organisation full of interrelated action to achieve a grand mission. There are no forums it sponsors to bring people together, no practice development discussions to share approaches or ideas. Nothing except a regressive check on what's happened.
I think you can get the picture. If a PMO is not building capability, bringing people together to develop expertise and find project relationships, then its not contributing to the value mission of the organisation. Change it, or get rid of it.