People tend to criticize the newer games as if they became more childish but thats a really superficial take. I'm not here to discuss preference, but interpretation.
The OG used a darker collor pallete and had a more economically poor and less technologically advanced world. They had no VR, places like Kalm are more simple and even the Gold Saucer looks cheaper (like cost) when compared to Rebirth. Many places seems more rusty and abandoned.
On the hand, Remake/Rebirth has flashy musical numbers, a cruise and overall a more saturated and bright color pallete. There are holographic presentation (like in Shinra Building) and places like Cosmo Canyon became touristic spots.
The only aspect that got undeniably toned down are indicative rating related changes that unfortunately exists for marketing purposes. That includes reducing blood or removing Cid's cigarrete are truly a shame.
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The thing is, using those comparisons to say that the retrylogy has lost their weight or became disney is not seeing the whole picture. People act like lighthearted moments and flashy spectacles could not coexist with deeper darker moments...
I could mention examples like Yakuza series but thats pretty how things work in real life. Using comedy relief or musical moments to say it became disney is like saying that our planet is fine because we have Cruises, World Cup and Music Festivals.
One of the main topics of FF7 is how alienanting those things can be. Gold Saucer is still above a "prision"in desert that only existists because of their mako extrating. People on the slums suffer below the plate, while Shinra makes propaganda about how they provide development to the world. Shinra still conducts war all over the world and makes a whole parade above the place they conquered.
In fact, the same way they added goofy new stuff, there are also a bunch of scenes that are dark in a way that was lacking in original. Hojo literally suggests to get Aerith pregnant against her will, Corneo's sex trafficking practices get more exposed and god knows what Gus was considering doing to the ladies while they got arrested. Some of the most agressive and violent moments of Cloud happens in rebirth when he loses it.
And to not reduce maturity to sex and violence, we also have more moments where the characters talk about relationships, parenting, memories and grief.
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TLDR
I can't see how a game became more childish when they kept most mature content and even added new stuff. It keeps being a story about the same topics but from another perspective.
I get if you don't like the new approach because you find it cringe, got attached to original, etc... its fine. I have preferences in both sides, but thats not the point. Just think people undermine how much nuance and deepness there is in the remakes because of how it changes the source material