Why is the Good Place so empty? As discussed previously, no new human has been admitted to the good place for the past 500 years. This really accents the difference between the real Good Place and the fake Good Place Michael was the architect for: there were more people, actually demons, in the fake one.
Michael becoming the Good Place architect makes sense. One thing his fake Good Place neighborhood got right was that it was never boring, which is the main issue with the real Good Place.
We now see the possible real reason for the Good Place Committee's inaction in the face of the breakdown of the judgment system — if the Good Place ends up being just as much a form of torture as the Bad Place then the issue is moot, and the inability of any new humans to enter the Good Place allowed them to hide the issue while trying and failing for 500 years to fix it.
Hypatia casually says "We try to stay current here" to explain why everyone dresses and acts like it's the modern day even though they all come from at least 500 years in the past. This isn't just a Hand Wave to make things easier on our characters and the costuming department though — since the biggest problem the Committee faced was the residents' overwhelming ennui, of course they'd be constantly importing new fashions and technologies from Earth as soon as they could get access to them to try to keep the residents engaged.
There's a subtle philosophy reference in Hypatia's introduction: Chidi mentions that he had a poster of Hypatia in his childhood bedroom - or rather a poster of Trinity from The Matrix with her face stuck on the top. Trinity in The Matrix is a follower of main character Neo, referred to in the film as "The One." Hypatia was a follower of Plontinus, who studied Neoplatonism which is an umbrella of philosophical ideas that basically posits all of reality is derived from a singular principle known as "The One."
