Gammadoodler
Hero
At a certain level, I don't think I'd argue there is even necessarily a virtue in "grounding" a D&D setting.Yeah, basically this.
The game cannot be realistic because, quite literally, it isn't real. It's openly not conforming to the restrictions of reality. Bringing up those restrictions in some places and happily ignoring them in others just feels arbitrary and capricious.
Fictional things, regardless of their level of realism, can still be grounded however. That's what differentiates most "hard" sci-fi from "soft" sci-fi, for example, even though both things are usually unrealistic. Gundam Wing is not striving for realism, because in reality there are no giant-mech pilots and it would be both extremely difficult and mostly pointless to construct such things. By introducing something unrealistic--Minovsky particles--however, the author was able to make a grounded and justified world that still managed to include things as unrealistic as Gundams. This is usually seen as being worthy of praise, as the Minovsky particles are a very minimal and narrowly-defined form of breaking from known reality, while still enabling all the fundamental story elements the author desired. The limits and applications of the particles are clear, and can't just be defied whenever one likes--they're not a free pass to do whatever you want. Similarly, stuff like Eezo and its titular Mass Effect are a very small change--just one exotic material, and even tying it into current ideas in theoretical physics e.g. dark energy--but that enables all the classic sci-fi concepts (FTL communications and travel, "shields," levitation, fancy material construction, even psionics). Such conservation of detail while remaining grounded is well-appreciated.
The thing with groundedness is, all it requires is some effort. Most things can become grounded; that's the reason we praise stuff like the above, where you employ minimal changes and don't break or ad-hoc modify the rules once they've been established. So the thing to look for, at least from where I'm sitting, is not "stuff that ought to be nerfed because it's unrealistic," but rather "stuff that I want explained because I don't see what grounds it."
The examples listed here "need" to be "grounded" because they are set in the Earth's future. Conventional Earth baseline is a baseline that is consistent with the fiction.
DMs use conventional Earth assumptions because it's the easiest thing to do; players understand Earth reality's rules, not because there's any real correlation between the physics of fantasy worlds and ours (in many ways quite the opposite).
You can just say "things just work differently here" and that is a perfectly valid, consistent, logical approach. The only work required is to provide the players with adequate guidance for their characters to make informed choices.