At present, Google Docs, Slides, and Sheets do not have a built-in accessibility checker. And while there are ways to improve the accessibility of Google Docs, Slides, and Sheets, they cannot always be made fully accessible to all users, especially those with certain disabilities.
Here is how to export to MS Word and check for accessibility:
Here is how to export to MS PowerPoint and check for accessibility:
Here is how to export to MS Excel and check for accessibility: