That’s a valid question! The app is intended for less tech-savvy people, as such, the terminologies used are to accommodate those users. “Upload” would rather be “Import”, while “Download” would be “Export”.

I’ve shared the use case in a previous Lemmy post:

This app is designed to compress smaller batches of images, aimed at casual users who need to compress and convert a few images at a time.

I created it primarily for friends and family who are less tech-savvy, to help them compress and convert images in a simple, safe, and private way.

Addressing the subscribing part; I had similar requirements, so I started subscribing via FreshRSS while using a custom theme to give it a YouTube-like experience.

I shared the setup a few month ago here: https://lemmy.world/post/21381606

Edit: One of the benefits of using selfhosted RSS with a web interface is that it is platform agnostic.