So Season 12 (or 9, the count is vague) has been a bit of a mixed bag for me, but i absolutely loved this episode. Granted, it isn't that the writing is that great, but overall and including the Themes and Throwbacks it's a solid 8/10 for me personally.
You see, "The Three Investigators" have a very special place here in Germany and they are very popular - i and many others grew up on them and i still love listening to the audio books. They don't take themselves overly serious and it's just innocent riddles. The homage Futurama paid them was just great!
Same goes for Tin Tin's Adventures, i've been glued to the comic books as a kid and they do a really good job there as well.
The last one fell a bit short, until Neil DeGrasse Tyson came up and had some really great one liners.
And well, LeVar Burton is just LeVar Burton. Awesome Episode for me, but i may be very heavily biased on this one :D
I thought it was great too. I especially enjoyed "cliffhanger manor". I don't think the writers will tie everything together in a later episode because it feels more and more like they are intentionally leaving cliffhangers everywhere as a joke. The joke being "you can't cancel us, you'll never know what happens to [insert favorite cliffhanger here]"