If the proposed solutions using OneDrive or PowerShell are not suitable then you may wish to consider 3rd party apps (e.g. here). Many of the apps offer trial licenses that can be used to export such a document volume without costs. Microsoft is keep to offer tools to move content into the platform but obviously will not spent much effort to develop tools to move away from the platform.
Is the number of items the only requirement or do you also have other requirements like keep original SharePoint modify date, export SharePoint custom metadata, only latest document version, ...
Paul | SLIM Applications (https://www.slimapplications.com/)