Moreover, Firefox makes it super easy to screenshot individual elements on a webpage, such as photos, by automatically determining the screenshot boundaries, which means I don't have to manually drag the screenshot area.

It seams to have a maximum length. If you try it on this page, it won't capture the whole page.

This is great. I wish I could add a clock to it somehow. This would be super useful for auditing purposes.

Fair point, but I highly doubt that this is how it's used most of the time. And taking 20 screenshots and compositing them in mspaint can be a meditative experience.

I would put money on it being the most common use case. It's certainly the reason I installed a screenshot extension for Chrome. I like the nod towards humour you've added at the end there, but it's probably time to cash out your chips and accept your losses.