Hey, I'm clearly not in the target audience, so take what I'm about to say with a grain of salt.

I think your motivation is great, I absolutely loathe these websites you mention and, if my mother was prone to doing these operations on her machine, I'd worry quite a bit.

By virtue of that alone, I believe this is a worthwhile endeavour and you should keep at it.

But to answer more specifically your points.

1. I don't know about the state of other GUI tools. Maybe the problem has more to do with exposure than lack of choice? I don't think more choice is necessarily bad, the real issue is managing to put it in front of the people you're targeting.
2. That goes to my second point. I could subjectively give you my opinion on it, but it would be better to have it tested by someone who fits the bill of intended user. I don't know how many of these people you'll find on Lemmy tbh.

Personally I... am not a fan of the interface but, I am a grumpy middle aged person who started on computers way too young on an Atari running Atari TOS... So my idea of a good GUI would probably send horror shivers down a lot of people's spines. There are objectively good points to yours: it looks snappy, reactive, there are not a lot of buttons or options so as not to overwhelm, and an easy and clear way to open the file explorer. Looks like a great proof of concept that you can keep polishing and iterating on as you go.

Good luck with it!