I appreciate rapind's point so I won't comment along those lines, but I think it's worth explicitly saying that the UI doesn't work within a certain screen width: it would display nonsensically, and I'd rather display an explanation to someone new to it (and the link to the GitHub ReadMe, which hopefully helps a little) rather than complete garbage. I definitely don't consider this a "feature" - I think it's just the least bad option, given the lack of a proper mobile view. It's also the case that the idea of "urgent access" doesn't work so well without data syncing - I generally wouldn't expect people to copy the export file to their mobile manually, in which case this won't actually have the data from another device.
It's probably true that a summary of features or something would be more helpful for those coming across it anew. In this case though, this is mostly for my own benefit, and it's explicitly out of scope to make money off this: I'd prefer to spend time on additional features for users (ie. me!), rather than implementing something like a product showcase or proper mobile view. Hopefully it's useful/interesting enough when it can be viewed properly, that it's worth coming back to.