Main problem: incredibly slow/unresponsive. Clicking things doesn't give good visual feedback and can take forever for the underlying webpage to load/reload.

It's designed as a webshop first and game library second (third, fourth?) Unintuitive UI, hard to search, hard to categorize, poor feedback on what's being downloaded and why. Basically every quality of life feature from Steam is missing.

But to be fair it's been a few years since I opened it. Might have improved a lot since then. I use Heroic these days. Also not amazing but at least it's open source.

Honestly, it used to have much, much bigger functionality gaps than it currently does.

The things all major Steam competitors are missing are value added features Steam has been investing on for decades. Those aren't basic or fundamental, but you may miss things like their controller compatibility layer if you favor a Sony controller or their metadata layer if you use that a lot. And devs do get value from their dev back-end, that is true (although console digital distribution systems have similar features these days, albeit a bit less streamlined).

I don't think that extra value justifies a whole-ass monopoly, though.