a very very good point. I think the answer is art. People like to create art. It's just another painting but we already have other paintings. Well this is a new painting that might speak to people in a new way.
Also I wasn't a fan of how every client looked like they were straight from XP. I used this as a way to get familiar with Electron, as well.
Lastly, it's open source so people can add whatever they want to it. I have a few ideas that I would love to be using myself (image previews, in-client file editing, etc), and I'm sure other people have their own features they'd want - and they can add them now.
You keep repeating this line. If a FTP client has received heavy usage and development since the XP days, that's a good sign, I think. It proves that it is well used, tested, reliable, and capable.
I'd much rather have a program with a passable UI that is lightweight and does everything I want, than one that has an unjustified resource usage to feature ratio.