DOOM 2 is one of the best examples of "more isn't necessarily better". They nearly doubled the monster roster, added an extra weapon, the levels are more sprawling, but yet it feels like a lower quality product.
>no episodes, so you never get a gear reset (which cheapens the thrill of finding items) and there's no tangible sense of progress that comes with chipping away at the game in little self-contained chapters with their own themes and story bits
>there are new monsters, but half of them just aren't all that fun to fight, and there are basically no bosses (since the "boss" monsters from D1 have just been relegated to fairly common enemies in D2) aside from the final boss: a fucking wall
>the super shotgun ruins weapon balance by eliminating the need to balance small arms fire with power weapons -- instead it's just a middle of the road butter sandwich that's "good enough" for 80% of encounters even if it isn't ideal for most of them, and you're showered in shotgun ammo so resource conservation rarely even comes into play
>has some legitimately great levels but they practically alternate with shit ones, and the middle of the game is a slog so painful that it stains the entire experience