A concept, in its complete form, rarely gets made due to limitation like you said but more than technical i would say it's more around scale and everyone in the team being "on the same page".
You can put into paper all the reaches of said concept and have some technical dudes translate it into work plans and divide the team into sections but we would be talking about a very intricate product even if it is a small project.
Wasn't that the reason the Final Fantasy games were called like so?
Also as a somewhat related note i was re-playing a game recently and thought back then that games in the Gen 6 were already pretty good and only needed to be scaled up rather than perfecting them, for example San Andreas in my eyes was already pretty good, only needed a map with more interactive things and another plot line for the sake of selling something new. IV in its initial concept tried to make a smaller map but much more interactive and with sideline activities, kinda like a criminal Shenmue, but they toned it down and we ended up with a sort of in-between, not as pure action fun like San Andreas nor fully completely immersive like Shenmue attempted but still was decent.
Sad to think Gen 7 went for the kike route of deconstructing and going towards mass multiplayer while Gen 8 was a further deconstruction not only of genres and icons but of the medium itself. Long ago those dreams of vastness reside, some examples did happen like Forza Motorsport 3/4 with the 500 something cars with interiors and customization on full HD which kinda achieved the only thing close to a Gran Turismo 2 on steroids many dreamed in the 90's with those HD cinematics.
The Sims 3 attempted (and mostly got) to make the original customizable Gesamtkunstwerk workflow Will Wright dreamed with the first game but deeply flawed due to its focus on sims rather than architecture/interior and, by far the biggest problem, being coded weirdly/dumb and having piss poor performance even with super computers of nowadays if you add more than 3 families more or a couple of mods even when many actually also work as performance enhancers.
Hell, still to this day people are expecting a Sims 3 remake made with real intention, some devs even said that game wasn't supposed to support expansions. I say this because it is widely rumored the current game, Sims 4, was actually a side project chosen to be the main one after a hypothetical catastrophe inside EA/Maxis residue studio, that or they went full jew