Yes, the admin can mass upload products for an individual seller in Magento2 Mass Upload marketplace. Under Marketplace Management-> Upload mass Upload Profile, the admin has to select Attribute set, upload CSV/XML/Xls file and Image Zip file, and then click on save for mass upload of the products.
The admin can mass upload simple, virtual, downloadable, and configurable product types.
Please do contact us for any further queries or requirements. You can also check our Magento 2 Extensions for additional features.