This thread really suffers from a critical lack of imagination.
It's just...not explicitly spelled out in the book ... You're supposed to make your own First Age,
Here is the thing. The problem you're objecting to here, the 'lack of imagination'? That is how we Got to this point. Not because people don't have good ideas for worldbuilding the First Age, but because there are zero reference points to attach those ideas onto once you sweep aside everything which came before. This is not a problem which started with the fandom either, its existed since First Edition.
There were three points in the entire setting which First Edition left entirely up in the air, with nothing save vague allusions towards what to do with them (in descending order of broadness): The Wyld, the Primordial War/First Age, and the Underworld. Between them, we have "literally everything and anything," "impossibly super-advanced beyond all frame of reference," and "old and unknown lands of former-Creation, apply your own death-filter." All three of these persisted as huge, looming question-marks until 2e, when they finally got books devoted to people sitting down and thinking critically about "what should
be here besides big signs saying Here Be Dragons?"
The first and last took cues from Creation and their respective splats, and though they Tried, were ultimately not outlandish enough to deviate from especially weird places in Creation colored by their major influences. A middlemarch forest of towering, blown-glass evergreens lit from within their heartwood like blazing lamps and bedecked in icicle-candles is a cool visual, but its a cool visual which exists independently of
being the Wyld. It could just as easily be a potent Fire demesne, an ifrit's cultured sanctum or a minor faerie freehold.
Not much different than a foaming geyser of superheated blood on a blasted plain which shoots out from the ground in gorily regular intervals, nonetheless capable of enwrapping an immersed ghost in a temporary, yet death-tainted body of warm and pliable skin. This exposure would be permanent to any living mortal, though the broiling steam will agonizingly strip away her old flesh down to the bone in the process. Is this curiosity, liable to let ghosts briefly walk among men as equals, or allow the living to be 'reborn' with a new face and form, an exotic Underworld feature or simply the results of a powerful shadowland?
Does it Matter? Ultimately, not really. Because the knowledge we have about the Wyld and the Underworld from a dozen and a half evocative examples is still enough to make even ideas like these feel as though they
could "fit" and "make sense" with the themes, even if only tucked away into a small corner and not made into full setpieces unto themselves. The First Age though, that was an entirely separate can of worms all together, since it exists as a Time Period and an Ideal rather than a concrete Location. There
were no evocative examples of the First Age at its height, only a collection of people, objects and places which exist Now in the Time of Troubles, but did then in far better conditions and or in more numerous amounts.
It had a collection of
Things which had to be there rather than a Theme, and you cannot ask people to "build their own" without first asking the questions of "what does the First Age
mean for this game" and "where do these things factor into it" to fill the void of that lack of evocative worldbuilding and
create that theme. At the time of Wonders of the Lost Age, the writers had only Magitech and "as the Second Age version, but not as shitty" to work from, not any setting-questions to answer, so they simply made more Things which iterated on what might be useful in a Second Age context. Even before Dreams of the First Age rolled around it was already set in stone that the Old Realm was about having A Shitload of Expensive Stuff, and many of its greatest treasures were Purchasable Stuff you could hammer together in your spare time if need be.
Which is a large part of why Dreams fell so flat, being bigger numbers, more things and Not All That Different, just Cleaner And Nicer. It didn't answer any questions people were hoping it would, and instead collected a lot of First Age Stuff in one place to try and stitch together a civilization from it without saying anything about it beyond "if your frame of reference for the Second Age doesn't apply here, use your understanding of the Modern day instead." And that is exactly how people interpret it now, once you take that "Magitech Stuff" off the table and demand people do it themselves. It makes that lack of answered questions more pronounced, because the book never
poses any new questions to stop and force the reader to second-guess those pre-established attitudes.
The only reason we ask those questions Now, and need answers to them Now, is because 1e/2e brought with it a wealth of contradictory information insisting the reader make sense of it all. If you don't have that context of 1e or 2e knowledge to try and reconcile, and the book says nothing on the subject, you're left with where the writers of Wonders and Dreams were at, but with even less to utilize because you cannot answer it with the solution of magitech. Which is not a failing of the reader, but a failing of the book to provide what is necessary to make it Work.
It does not
ask the potential Storyteller, "is your First Age a utopia built on mortal servitude? Exalted hubris? Technological advancement?" "Are its Solars truly the tyrant-kings they were portrayed to be, ignorant but well-intentioned rulers in ivory towers, or unwitting victims of a jealous coup by an overly alarmist Sidereal junta?" and so on, because those will be the things which shape the themes and focuses of "this is how the First Age was" ingame more than any establishing-paragraphs about farming arcologies and how abundant the hand-manufactured lightbulb was. So until the text Does take explicitly-noted steps to
make those gestures, and give the reader something which can Inspire them to work out the kind of First Age which is not a reductionist magitech cybercity with a fantasy cast, or cleaner-and-nicer Second Age with some spit-shine on the ugly parts, it is selling an Empty idea of "make shit up to solve these setting-gap problems."
You can't just demand imagination in a contextless void of "not this, but not the other thing either." Because inspiration doesn't work like that, the book has to Teach what the First Age should encompass before it asks the reader to define it for themselves.