Let's see things from a different perspective. I already own the D&D Basic Set, the Rules Cyclopedia, the 1E MM, the 2E MM, the 3E MM, the 4E MM, and the Monster Vault. I have seven different descriptions of what a Kobold is. Why would I need another one? I can just read any of these entries and come up with the crunch numbers on my own. What's in it for me?
Quite apart from the "crunch vs. fluff - which is more interesting?" discussion that has been a topic for debate for years and years...
If you've got seven different descriptions of what a Kobold is, what do you need another description of a Kobold for at all? Couldn't you just tweak kobolds to match up with what you liked best about them in the editions of your choice?
You might argue that you shouldn't have to tinker with monsters to make them interesting, but you don't
have to - you can either use the "boring" Kobolds as written, or avoid them entirely. Not to mention that what's interesting to me isn't necessarily interesting to you, and vice versa. In the absence of WotC somehow snagging the Platonic ideal of Interestingness and forcing it to write the Monster Manual for them, we were never going to get a book of monsters that checks every single person's "interesting" box. But the fact is that you rather easily
can graft a breathe weapon onto them or splice the kobold features onto the NPC assassin or cultist or what have you with minimal mechanical blowback. You might have to up their CRs a little bit but the fact that with two minute's work you can create Dragon Heritage Kobolds, Kobold Stalkers and Kobold Shamans makes for a rather mechanically diverse and intriguing game in my opinion, and without sacrificing the ease-of-use that's such a major selling point for 5E.
The design decision that was taken with Kobolds was what someone earlier in the thread said - they're the trap-using monsters, and if you ever corner them they'll die in short order because all they can do is hit you, and they're not terribly good at it. Kobolds
are that, at least if you're going by the Monster Manual as written.
That's the crunch. They've provided the HP and the abilities there for you - the rules for traps and little clay pots of acid etc. are provided elsewhere and don't need to be included in the monster stat-block. You might disagree with the design decision here, but it's a perfectly functional monster and the tactics they use are plenty to differentiate them from other monsters like goblins. I'm sorry that it doesn't check your "interesting" boxes, but if you're not looking to adjust the material to suit your tastes, you're not going to get very far in
any edition of D&D - and if there
is an edition of the game that near-perfectly lines up with your tastes, then I'm immense jealous of how lucky you are! I'd say 5E is pretty close to being that game for my own tastes, but there's still things about it I know I'm going to want to house-rule or homebrew, once I've gotten a little bit more actual play under my belt.
It's clear you're otherwise invested in 5E, or we wouldn't even be having this discussion - if you've got seven other versions of Kobolds to choose from, if the rest of 5E didn't interest you you'd presumably be playing one of those games instead! Maybe you like how fast combat runs in this edition, maybe you like that there's less book-keeping than with previous WotC editions, maybe you just like the funny disclaimers WotC is putting in the beginning of the books. But one of the strengths about 5E that really appeals to
me is precisely how conducive it is to tinkering.