Thanks! This pinpointed the issue - I went into the package contents and temporarily removed the "patches" folder within the Logic app, reducing the library to a handful of legacy patches, and the library refresh rate was much faster.
Two new questions:
1) What is the computer spec metric that would theoretically speed this up? RAM? GPU? I'm on an intel machine, but I wonder if a silicon machine would not have this issue.
2) I have noticed that in Logic 7 onward, upon selecting a new track, the library will turn blank for a split second before refreshing (you can see it in the above GIF). I understand they made a few changes to how the library works (one being that "enable patch merging" settings reset on each track selection and are not global as they were previously). Do you know anything more about this change? I had long wondered if the library turning blank for a split second had something to do with the added lag.