I would even venture to say the average user also finds Calibre complex. Would you mind taking BookFusion for a spin?
We have uses with over 30,000 eBooks in their libraries and will be able to support your collection without issues. BookFusion allows you to easily upload, read and organize(tags and categories) your eBooks.
Your entire Calibre eBook collection will be available across all your devices while keeping your bookmarks, comments, highlights and reading progress synced.
I'd rather not. The beauty of Calibre is that you run it locally, or on your NAS (with Calibre-Web). If I want my dat in "the cloud" I'll just buy some Kindle device and be done with it.
We have uses with over 30,000 eBooks in their libraries and will be able to support your collection without issues. BookFusion allows you to easily upload, read and organize(tags and categories) your eBooks.
Your entire Calibre eBook collection will be available across all your devices while keeping your bookmarks, comments, highlights and reading progress synced.
More at https://www.bookfusion.com/reading/cloud-library
We even have a Calibre plugin that will allow you to easily sync your entire collection or only eBooks you are interested in.
https://www.bookfusion.com/reading/calibre
PS: I am the founder of BookFusion