While the Horde definitely did get the better end of the Allied Races stick for the most part, the Vulpera vs. the Mechagnomes is just the most recent and most lopsided example.
Vulpera are cute, fuzzy wuzzy animal people. Cute little animals are the closest thing the internet has to an official pantheon. Forget neo-paganism - Ancient Egypt worshiped cats, and the eleventy squllion cat pic, vids, and memes show what a true ancient religious revival looks like.
Mechagnomes, meanwhile, are a flavor of a race so inconsequential they were evicted from existence in WC3.
That said, Gnomes both badly needed and were grossly overdue for new content and exposure, and Mechagon turned out far better than I would ever have thought. The fact that we at least got a patch of exposure and content to them before they were plopped into the game as a playable race puts them well above the screeching blighted nonsense that is the Void Elves. While some of the implementation could have been better, as a whole, Mechagnomes are hardly the worst allied race.
But still, this was never going to be an even comparison holding them up against what the Horde were given at the same time. Vulpera have weaponized levels of appeal, while even adding “Cyborg” to their resume can’t push Gnomes over the fact that… well?
They’re still Gnomes at the end of the day.