I went back and watched it again for the first time since it aired. I was not a fan of the show, mostly because of its disjointed approach and the selection of the source material. But I agree, it is an overly depressing and somber show. Some will claim that the nature of that war made it necessary to emphasize that tone but I disagree. The music is very dramatic and sounds like a funeral. Characters pause to reflect on life and death in the middle of the battle and actors spend too much time staring at the horizon or directly into the camera.

But if you take into consideration the numbers, after the initial losses, the Americans won almost every battle in the island hopping war. And there were, if I am not mistaken, fewer deaths than in the European theatre.
You are mistaken. If anything the pacific was much more bleak than depicted. per soldier fighting casualties and deaths in the Pacific were higher for US soldiers.
Just consider that a) the Japanese killed 30% of US POWs while the Germans killed 2%; and b) the massively higher proportion of close quarters and hand to hand combat the US pacific forces had to engage in.
here is a rough comparison:
Weather
Pacific: 80+ degrees, 80%+ humidity, sudden rain fall that can cause flash floods
Europe: Snow, drenching rain, biting winds, -20 or more degrees, summer not so bad
Enemy
Pacific: Japanese fight to last man, kamikazes, banzai charges, they'll mutilate, torture, eat, and rape marines, caves and tunnels under ground, ambushes
Europe: Germans surrender in the thousands, some fanatical, actually see Americans as humans and will talk to them, less hate between Americans and Germans
Navy
Pacific: Thousands would be torpedoed, go crazy in the water, and get eaten by sharks
Europe: Beware of U-boats and weather, sucks if in Merchant Marine
Wildlife:
Pacific: Have one waking up with a worm in your pen is and having to get it out with bamboo tweezers. Plus poisonous snakes, frogs, spiders, mosquitoes, tigers, crocs, leeches etc.
Europe: Nothing hazardous, lice?
Battles:
Pacific: Thousands of casualties on a few miles of land, always have to storm a beach, jungle is an enemy within itself, take hours to chop your way a few hundred yards, everything is hidden,
Europe: Huge ass battles, forest with trees exploding, crossing rivers in wooden boats, taking hills and mountains
POWs:
P: 30% of dying, hellships= drinking your own piss and peoples blood, starving, torture, forced heavy labor,
E: 2% of dying, march in snow, freezing, get shot at by your own planes train, but Germans didn't really torture you
Combat:
P: Hand to Hand, actually killed and saw the enemy, impenetrable defenses, had to use flame throwers, tanks couldn't help that much, infantry had to do everything, if you were sick or wounded you'd still have to fight
E: Tanks and air power, almost never hand to hand, 100 men to kill 1 German, Germans had better tech and vehicles though, GI's would go on patrols and capture germans, you get frost bite you go to the hospital
End of War:
P: Okinawa and Philippines worst battles, Japan invasion= 2 million casualties and war will end in 47 or 48
E: Germans surrender en mass, mostly Russians fighting in Berlin
Supplies:
P: Marines got worst food, obsolete weapons at first, not many tanks, 84.3 pounds of gear, would starve without water, had to march everywhere
E: Army got the best equipment, but got winter clothing late, could ride in vehicles, no jungle
RnR:
P: Went to Pavuvu or some isolated island.
E: Bars and clubs, civilization, cities
Defenses:
P: Navy could not knock out defenses
E: Atlantic wall no problem, siegfried line taken, hedgerows burned, at least the defenses were passable and destroyed