I looked at the contents of the Voyager Golden Record a while ago (at https://en.wikipedia.org/wiki/Contents_of_the_Voyager_Golden...). Frankly, it's underwhelming. There's lots of arbitrary sentimental data that will make very little sense to another civilization, no matter how smart they are.
It appears that it's more of a message to ourselves, demonstrating our cultural diversity.
The first few images stored on the disk are interesting. They establish our location in the Milky Way as well as our math and physics.
I think you underestimate the impact space travel had on the collective consciousness of the part of humanity that was aware of it. What you flippantly dismiss as diversity wasn't a thing back then, not like it is now, and both the reality and the dreams of spaceflight - even unmanned - brought with it a strong sense of the whole world being one people. To prior generations that was almost unfathomable.
Disagree about it being underwhelming or arbitrary.
You're right about it being a message to ourselves though. There's an essentially 0% chance that anyone other than humans will ever experience it, and a 0% chance that we'd ever know if they do. Still think they did a good job.
I've really enjoyed reading about the disk, and feel that they executed well on the concept - especially given the limitations of the media. It may have struck a good balance between what would be too simple technologically and not communicate much, and something which would be too complex technologically, and could be difficult to decode. The contents show a variety of what Earth looks like and sounds like, and some of our most basic concepts with regards to math and physics. Communicating more complex concepts within math or physics could be severely constrained by having to introduce the required notation in an intuitive way.
What better could we have chosen to communicate, given the same limitations of format?
By biggest objection (assuming that the disk is actually intended for aliens, which I do not think it actually was) is the the technology to encode the data, but what content we chose for the limited space.
For instance, consider the "color" images we included. In reality, each color image is actually just 3 black and white images taken with slightly difference response curves. Granted, the solar spectrum image should give them enough information to determine these curves; but, unless they have an identical visual system to us, they would still not be able to reconstruct what they would see as a true color image. If we really wanted them to see in color, we could have chosen more appropriate response curves to take our images from. Regardless, the space would have been better spent including more images. However, from a PR standpoint, including color images was likely a very good move.
Simmilarly, I do not any justification for including spoken greetings. Assuming the correctly decode them as sounds (which I think is reasonable), and understand them to be a language (less reasonable) I don't see how they could decipherer anything meaningful from them (except, perhaps, the phonetic inventory of human languages). Similarly, I would expect aliens to do little more than scratch their heads at the inclusion of 90 minutes of music.
The point about color images is interesting. Although they might not be able to deduce the exact wavelengths in which the image is encoded, they would very likely be able to understand that the colored image layers are connected, as the layers correlate highly in their spatial structure. In the same manner that we use artificial coloring to better understand astronomical images, the color information on the disk provides more information when viewing the images, which could make the images more interesting for their study.
For the spoken language, there is likely not enough information to decode its meaning. But its inclusion together with images of us might lead them to understand how we communicate by voice. The sounds of animals and humans may be similar to other lifeforms discovered. Music as well may be something which is common to many forms of intelligent life. It would probably not be possible to understand much of the contents, but observers might be able to relate to the emotions in the music (even though they may not map directly to ours). In any case, with art much of the value lies in the interpretation. As long as content is presented which they would care to judge as art, they may see value in it.
Well they could've used an early version of SGML, the text encoding we still use after all these years ([1]). Would've confused the sh*t out of them aliens :)
You should also look at the pioneer plaque (https://en.wikipedia.org/wiki/Pioneer_plaque) which I think is pretty amazing. The concept of how do you begin communication with someone that you don't know is a tricky one. The cover of the record also has to provide a decoder for the record, also not trivial.
The first few images stored on the disk are interesting. They establish our location in the Milky Way as well as our math and physics.