Hold on, there's a much bigger issue here: It works very poorly because it's being misused. The Quote template is only meant for very short quotes, which should never come remotely close to what's happening in the Foucault Pendulum article. That's why the text is centred by default (and why forcibly aligning it to the left makes it look terrible).
As per the
Quote template's description,
This is useful in articles where you are short on images and want to add some sort of graphic, or you just want to set off an important or interesting quote away from the main text.. It's supporting content, not the meat of the article. For anything longer, these will always look clunky, because they're over-decorated.
The Lyndon B. Johnson quote in
https://wiki.tfes.org/The_Conspiracy is about the longest I would expect for it.
However, I do agree that the margins were excessive, especially on mobile. I've reduced these considerably, but left the text size at 90%. As time goes on, I hope to evolve that template into something prettier, but, again, for very short quotes only.
My suggestion is that large quotes or entire paragraphs from books shouldn't be in a box - the decorative effect is to a detriment of long-term readability. I can look into designing a template for long-form source references the long term (or you can create one yourself - templates are just pages, more about them
here), but the immediate solution is to stop using this template for anything longer than a handful of sentences.