I do assign weight to the second: that an engaged, creative player working with an engaged, creative DM could meaningfully play a monstrous humanoid such as a hobgoblin or gnoll, and help contribute positively to an overall story. I therefore thing gnolls should be supported -- that a half page of published real estate be given over to this option, given that there are many who *like* the mechanics for playing gnolls (I'm one of them).
Well, to be clear here... I think you missed the point. The point is that hobgoblins and gnolls are not equally monsterous.
Hobgoblins, as being presented in the current lore, aren't really particularly more "monsters" than dozens of human cultures that have existed in human history that were far from sympathetic or fair in their dealings with others. I mean, yes, you could call that a "monster" i.e. Spartans, Samurai, Mongols, Huns, Cossacks, Nazis, etc. were "monsters"-- well, no doubt so in the eyes of those who found themselves on the wrong end of their spears, but when used in that context it is understood that it refers to moral standing.
Now, in the lore they are going with for Gnolls... well, they were just normal scavenger/predatory animals until they caught a magical disease that transformed them into mad, ravaging creatures bent on destruction and devouring everything and everyone. So this is a totally different monster-- not just 'you've been raised in a sociopathic warrior culture' and rather 'your fundamental purpose for being is to do bring evil into the world'.
If you have a Drow, an Orc or a Hobgoblin-- it is entirely conceivable to shift their alignment to good while still maintaining many aspects of their cultures that still make them.. well... them. Drow can still be underhanded, charming, political and highly religious, Orcs can still be short-tempered, overbearing, daring and primitive and Hobgoblins can still be disciplined, honorable, task-driven and coldly rational. They can still retain those flaws and remain identifiably those races.
(Actually, I really have no idea why you chose Hobgoblins as your example-- they are probably even more human than literally anything else you could have used as an example, including Drow. I suppose because of the lack of any examples of the race being used as a hero in pop culture?)
Problem is that if your definition of what a Gnoll is states first and foremost that they are demon-worshiping creatures of destruction who simply seek to see the world burn... well, that's not really something you can have a good version of.
But, again, that all depends on how the setting is defining what a Gnoll is besides being a 6+' tall furry beastman.
Isn't that the whole thing with D&D? It is a system first and settings are modular. There is never any guarantee that anything stated about any of the PC races or monsters in any of the core books absolutely has to or even should be true in all settings. Which certainly creates an issue regarding what should be written there at all.
And yet... books don't have infinite page counts. Obviously not everything imaginable can be put into a single book. So something was always going to be left out. In this case it was continuing the Gnolls as PCs that was done in the end of 3.5E as well as in 4E.
Though... given that the only evidence we have on the issue suggests that there was a significantly larger demand for Gnolls than there was for Firbolgs, it wouldn't be entirely out-of-line to accuse WotC of ignoring what the customers actually want and instead churning out only what strikes their own fancy.
The best solutions would have been either
1) Include the stats for them in the book regardless with the caveat that it is not recommended that they be played in a typical campaign if you are playing them as described in the book. Kind of weird-- it requires expressly rather than implicitly acknowledging that everything written on the previous pages is not going to be the way they work at every table.
2) Simply stat that while no PC stats are being given within this book as it primarily focuses on the current edition of Forgotten Realms, there are literally dozens of races in different worlds that aren't going to be covered here and Gnoll PC stats may be included in a future release for the Gnolls of that world.
Already, inherently, you have to realize that this sort of book by its very nature... everything it covers, it is going to "One True Way" it. It is pretty inevitably going to present Goblins as though they are all one exact way with one exact set of beliefs and one exact set of customs and traditions and specialize only in one particular thing... despite the fact that Goblins are so damn ubiquitous everywhere in D&D in every environment across the world with virtually no communication between tribes and heavy influences by the creatures that live around them... that the very notion that Goblins would all be the "same" is absolutely ludicrous. If one thinks the diversity of Elves is insane, Goblins ought to be 100 fold so. Cavern goblins, forest goblins, desert goblins, river goblins, deep goblins, sewer goblins, mountain goblins... there really ought to be very few things one could say that would be true about them universally except being small, short-lived, fast-breeding, ugly and selfish.
But, instead, I bet you that we are probably going to have a single stat block, likely without any subraces (unless they do something monumentally dumb like try to force Hobgoblins and Bugbears to be subraces despite the three having virtually nothing in terms of abilities save for dark vision in common) and will present them as though not only is every tribe in every environment in every region exactly the same, but probably go so far as to suggest that every single individual within every single tribe is virtually exactly the same... and probably claim there is some list of classes that no Goblin in no tribe would ever be proficient at despite... well... again, they are short lived, adaptable, fast-breeding and live everywhere being easily influenced by everything, so that just couldn't be true.
But, at the same time, if one is trying to fit 30 races and 100 new monsters into a single book, just how would one go about presenting any sort of depth or breadth to any of them? All PC race write ups have this sort of issue.
