I solved the problem, and it turns out it was a rather ironic solution. I identified above that my saves were quite frequent, totaling well over 2000. This is a pattern I have in many strategy role playing games, especially those in early access. This pattern has never been the source of performance issues. However, I theorized that the sheer quantity of saves that the game was trying to deal with and have readily available to me was actually causing the performance issue - although, it seemed unreasonable because in my limited knowledge of game development, I don't see how the two are related. Still, I deleted almost 1900 save files, keeping the most recent few files from each of my previous playthroughs. That fixed the long loading times instantly.
So! In short, do not create too many unique saves because it will give you performance issues.
