Godot? Wtf?

Also,

I’ve looked around, and I found all the local GUI converters like Handbrake are unwieldy to use, especially if you just want to convert in bulk.

Idk Handbrake specifically, but generally when that kind of thing happens it's for a good reason. There are a lot of options when converting a video file, and you can't support them all without exposing that complexity in some form. If you don't think so, then you haven't done enough research into the problem space.

With that said, a "dumbed down" version of Handbrake that is optimized for a single common use case could be useful. For example, re-encoding iPhone videos to minimize compression artifacts when sharing over Whatsapp could be useful to people. However, I don't think a desktop app is the most accessible implementation for that.

EDIT: also, even if a desktop app was a good choice, it might be more practical to implement it as like a preset for Handbrake rather than a whole separate app. My mom isn't very tech literate, but I could probably teach her how to activate a preset (idk if Handbrake supports presets, but it probably does lol)