A full six years ago, Shamus Young argued that survival mode was basically just “creeper mode,” because the threat of the other monsters was so overshadowed by creepers that they were basically a non-issue. After half a decade and then some, this is still a problem. Zombies and spiders remain almost completely a non-threat (past the very early stages of the game, when brand new players might find themselves getting sucker punched by them at the first nightfall, totally unaware of how to build an effective shelter before then), and skeletons remain dangerous only in large groups or possibly when picking a player off as they flee creepers in a panic. New monsters have been added, but none of them come close to overshadowing the creeper.
I blame memes for this. Once the creeper became a meme, messing with it in any significant way became a bad idea. Once it became a meme, people wanted Survival Mode to be Creeper Mode, or said they did anyway, and never mind how much better the game would be if the creeper were one component of an arsenal the monsters had to throw at players (it doesn’t help that the game’s fanbase are twelve-year olds, who love memes more and understand less how much better a game is with depth as compared to older demographics).
Zombies are relatively tough, but not very quick and can only attack in melee. Skeletons have ranged attacks, so there could be a balance between the two where zombies are easy to avoid but hit hard and keep the player occupied, smack the zombie to bounce him out of melee range, wait for him to run back into range, smack him again before he can deal damage. A fairly simple timing trick on his own, but in large numbers it’s harder to keep them all timed, and if there’s a skeleton peppering the player with arrow fire all the while, that means the player either needs to tank through those arrows while cutting up the zombie before closing on the skeleton, or else they can try to outmaneuver the zombie to get to the skeleton without killing the zombie first.
This resembles the current interaction the two have with one another, but there’s several key deficiencies that prevent them from really synergizing with one another. For starters, zombie attacks don’t hit very hard. A leather chestplate, something a player can assemble day one if they’re reasonably lucky with cow spawns and drop rates, can absorb a zombie attack altogether, so it’s not very threatening to run past the zombie and smack the skeleton. The zombie’s two armor points do basically nothing against even a stone sword, a weapon trivially easy to acquire in the early game, and it has no more health than the skeleton. This is both because skeletons are too tough to serve as a glass cannon and because zombies are too fragile to serve as an effective tank. Skeletons, rather than being a complicating factor in a fight with a zombie (or spider), are basically just a flat upgrade to a zombie, almost identical but with the ability to fight at range.
Spiders likewise are just downgraded zombies, with less health and less damage. In theory, a spider’s thing is that they can climb walls, but the game is Minecraft, so generally speaking a player’s fortifications will be fully enclosed rather than just being a wall. The basic idea of having a mob who is weaker but has the ability to circumvent fortifications would be good, the problem is that the spider does not actually have the ability to circumvent the most common fortifications of the game.
The monster that actually has this ability is actually the enderman, who can teleport. Now, the enderman is also a lategame enemy who only spawns very rarely in the starter Overworld, but a weaker monster with the same trick would be a valuable addition to the game. Not strong enough to rip a player in iron armor to shreds, but enough of a threat that there’d be periodic “dammit, another one got in my house” moments during the night.
Side note: if the enderman wasn’t such a late entry to the game, I imagine it would’ve been the monstrous mascot rather than the creeper, as it’s far more memorable and encounters with them tend to be much more dramatic. They’re relentless, hard to escape, hit hard, have tons of health, and their visual cue is far more terrifying than the creeper’s on its own merits (I freaked the fuck out the first time I heard it). The only reason the creeper’s hiss is more panic-inducing is because of how aggravating the associated creeper damage is. Unlike the creeper, which ambushes the player and either kills them or not in about two seconds flat, the enderman will have a deadly and proper-length fight. That fight will only last about 10-20 seconds, but that’s enough time to smack the baddy around a little, realize it’s ripping up your health, attempt to make a retreat, and get caught on the way out. There’s an arc there, not just hisssss-BOOM and you’re dead after a single moment of panic.
Then there’s the creeper. Creepers could be siege breakers whose main role is to blow holes in defenses to let the other monsters in. As it is, they’re too beefy and deal too much damage. Their high health means it’s difficult to respond to the hissing by just flat out murdering them, and the damage they deal means that until the endgame, getting caught in a creeper blast is lethal all by itself. Even in the endgame, the response to being caught by a creeper blast is not “oh, no, now a bunch of other monsters are coming through the hole in my defenses” but rather “oh, no, I just lost 80% of my health just now.” No other monster who can do that spawns with anything near the frequency of the creeper. Every other monster is a schlub who barely merits consideration, and creeper fights aren’t even interesting.
All that and they can survive in daylight, too.