Some World Heritage Sites loom large and will stun and wow people no matter who you are or where you are travelling from. I think of my time at Victoria Falls or Jerusalem and how immediately accosting those were. Aranjuez is not a site such as those, and that's okay, it's in the "majority" of sites. Aranjuez, like many of the historical cultural sites, will vary in what it offers to the visitor based on how much you effort you put into learning about it.
So what is Aranjuez?
Aranjuez was the "summer palace" location that the Spanish monarchs would retire to in the 1700s and 1800s. It has a quite massive aforementioned palace that was expanded over time, as well as a large garden/park that still exudes immense beauty, especially during the warmer months. There is a waterway that was artificially built by the monarchs so they could have boating events near the palace, and the original city center (which is removed a little bit from the palace) was originally designed to only allow members of the royal court to reside there. As a result, Aranjuez becomes a bit unique following such an "exclusive" royal history.
What type of background you come from may color how you experience Aranjuez.
Perhaps you've never been to Spain (or maybe even Europe!) before and this is one of the first handful of sites you are seeing. In that case, you're going to love Aranjuez. The size of the palace will awe you with all of its unique rooms, and you'll find the garden a delight to walk through.
On the other hand, perhaps you've seen a lot of Spain already, and have visited a ton of Spanish palaces. In this case, Aranjuez will still be nice, but it likely won't blow you away or surprise you with something significantly different than you've already seen. A lot of Spanish royal palaces were designed similarly, and the flora and fauna in Aranjuez is beautiful, but typical of what you find in much of Spain.
As for my own personal story, I loved Aranjuez! I visited it in November 2024 in my second of nine months living in Spain, and the ex-royal town made a perfect cute little daytrip from Madrid. I loved the signage inside the royal palace showing how it developed over time, and the guided tour was well worth taking. (However, I had an advantage as I can understand Spanish.) I was surprised at how great the adjacent gardens still were, even in the late Fall. based on personal experience, I recommend passing by the Visitor's Center at the beginning of your day to get a map of everything available to do. I only learned about the history of Aranjuez while on the site, but I can definitely see how much more I would have been able to get out of it if I had time to read up on some of its history beforehand.