No it’s not.
It is grim dark to have people’s insides on the outsides for a few different reasons but the time you get a few episodes in, and have some of those insides be inside someone else as well. It was like a running theme.
Space 1999 was just as dark as Discovery is, and it was on network TV in the 70s. Disco is hardly grimdark.
Nonsense.
For a start, it’s time and place of production wouldn’t allow it. But if you can find the on screen eviscerated cadavers and lopped off heads, go ahead.
I always think it's interesting when Star Trek fans complain about "grimdark" or violent Star Trek (or dark anything like sets, etc) in the modern era.
Look at what is almost universally considered the best Star Trek / fan favorites:
MOVIES:
Wrath of Khan (A violent revenge story, bloody, murdered corpses, torture, main character death, pew-pew, explosions, people burning to death, jarring and lingering body horror, spaceship battles resulting in horrible graphic deaths, militarized Starfleet, mid-life malaise, zero exploration, etc)
Undiscovered Country (Politics, war, assassination, murder, cover-ups, conspiracy within the beloved and precious Federation to perpetuate conflict on a galactic scale, racism even amongst the main characters, pew-pew, explosions, zero exploration, alien blood by the gallon, and a very dark and dreary color palate)
First Contact (Extremely dark lighting, 1000's dying in a pew-pew space battle, nuclear holocaust on Earth, zombie / body horror, principled main character losing his perspective and crazed for revenge, pew-pew phaser battles, explosions, crew members meeting horrible fates, digging into a dead corpse by hand to extract technology, Starfleet making bureaucratic decisions, zero exploration, etc)
Into Darkness (Admittedly polarizing but with a lot of fan support, here we have non-stop action and destruction, looming war, evil power-hungry Starfleet Admirals, explosions and pew-pew everywhere, conspiracy, paranoia, sabotage, skull-crushing and Section 31)
TELEVISION:
TNG Conspiracy (Often viewed as one of the better early episodes. Claustrophobic atmosphere, paranoia, body horror, blood-and-guts violence, disregard for alien life, etc)
TNG Best of Both Worlds (Unstoppable and irredeemable adversary, pew-pew action pieces, death and destruction, etc)
TNG Yesterday's Enterprise (Klingon War, dark and foreboding lighting throughout, conflict, violent death, pew-pew action, explosions, dreary and joyless, etc)
TNG Chain of Command (A hard-ass captain, looming war, conflict between officers bordering on insubordination, physical and psychological torture, unpleasant nudity, clandestine operations)
DS9 Series (DS9 is a heavy fan-favorite with a very loyal following. Here we have all-out devastating war, a darker visual style, Starfleet battleships, politics and scheming, pew-pew fleet battles, explosions and phaser battles, serialization, melodrama, very little boldly going or exploring, terrorism, Section 31 galore, conspiracy / paranoia / power games at Stafleet's highest levels <Homefront>, and the "top episode" <Pale Moonlight> about moral and ethical ambiguity of a Starfleet Captain)
ENT S3 (Considered by many to be when the series found its legs, this is a turn to serialized post- 9/11 conflict, Earth attacked with millions dead, moral ambiguity, torture, pew-pew, conflict, etc)
Then, if you look at the films, for example, that were more bright and about exploring / alien life / character stuff (TMP, TFF, BEY), those have generally not done well. So...I don't get the disappointment or anger about the look/feel/themes of some of these newer iterations of Trek. The powers that be are giving us
exactly what we've told them we want. So, I kind of have to say "give me a break" to that line of complaints.