Studios have done it before. The question is where Square is going to choose on placing their attention. Final Fantasy XIV is a perfect example of how much you can accomplish when you aren't afraid of sacrificing a little bit of fidelity for the sake of actually delivering meaningful content.
TBH FFXV is a decent example of this too. The environments in FFXV honestly weren't built out of super amazing assets....the best looking parts of the game were a result of clever placement and usage of lighting effects. It wasn't something like GTA5, Horizon ZD or RDR2 tier but what was there absolutely worked for what they needed it to....they just canned too much of the game.
its not about paying attention or not. Game development never been that easy and simple. FFXIV is not good example, because its more than sacrifying visual fidelity... if you watch the noclip documentary, you can see how much devs actually bite their teeth to follow the scheduled of 2 years development 2.0 and later each expansion. In the interview even Yoshi-P telling how staff coming back to him. Also, put aside the visual fidelity, but unless Nomura staff develop the sequel with XIV visual fidelity which is LOL.... dont forget XIV visual is getting outdated fast, its ps3 level of quality obvious there difference in development process there and allthough if Nomura team downgraded the visual bit, like XIII sequel but the scale of making content is still whole different there...it wont be exactly same...FFXIV asset even developed with very lower resolution..its like ps360 era of texture..even latest expansion still developed with that kind level of textures..surely will take longer time if they trying to make higher quality than before...obviously VII Remake wont have ps3 level of textures..not to mention it would have better animation, physic simulation and world simulation compared to XIV. For XIV they didnt even have manpower to release opposite gender of latest race, and even updating old textures..the game even lack of voice over and they reused same animation over and over again...they already had handsfull. Its not 1:1 comparison.
The environments in FFXV honestly weren't built out of super amazing assets....the best looking parts of the game were a result of clever placement and usage of lighting effects
i dont know how you can said this..the game still one of the best looking open world game out there..as i said, making asset is one of most process that that long time in game development..if you watch the making documentary you see how the team travel far to gather data for the game. FFXV also example of this is not that simple...with the open world that actually not much to it, still that take 4 years to develop, FFVII with lot of area, unique location which is as i said before, you cant simply copy paste or put placement of object like other open world game included XV..its not that simple...there even more the to game visual than 'clever usage of lightning'...game development not that easy...while dont forget FFXV didnt actually had much city to explore, Tenebrae not even explorable, Altissia and Lestallum is only city i recall explorable although nothing much to it, the rest? the devs even resulted turn half part of the game as linear train section because they didnt even have time. They even cover up content with DLC. XV not even good representation since it the content it had even lacking, comparing for example you want to remake VII without cutting content like XV did..you want the game end up like XV? Junon end up barely explorable and half end of the game suddenly become linear , lot of open area not explorable like outside train section in XV? Luckly we get Midgar section although the game become part by part atleast they not drop it or turn it to cgi movie like insomnia invasion and rest of content into anime and dlc.
even botw with lower visual fidelity, lot of reused asset and content, developed for console basically 'pro' version of xbox 360 still end up take 5 years. Its not that simple..still need lot of resources.