So, it's the 4e designers fault that no previous design team at TSR/WotC could make gnomes popular enough for more than a few players to like them. Right.
That is not what I'm saying. Each design team had opportunities, and must take their blame in turn.
1Ed Gnomes were essentially short Dwarves. They did some things better but most things worse. Main advantages- they spoke to burrowing critters at will and were able to cast MU [Illusionist] spells. (1Ed PHB p15-17)
2Ed Gnomes were much the same. (2Ed PHB p20-22) Some racial variants could do things like ID potions by scent or had skills in making gizmos.
3Ed Gnomes continued the trend of being lesser Dwarves with a knack for Illusion, and had their communicative abilities reduced from at will to 1/day. They also lost the saving throw bonuses they shared with Dwarves
3.5Ed Gnomes had their favored class changed to Bard, considered by some to be among the weakest of the 3.X classes (esp. in comparison to the 1Ed bard who was something to be feared).
Each of those is a design choice that could have been done differently.
I knew a lot of 1Ed gnome players, not a lot of 1/2 Orcs. In 2Ed, 1/2 Orcs got a little popularity boost. In 3Ed, there was a modest decline in both, which for Gnomes accellerated with the 3.5 revision making Bard the Gnomes' favored class (this is all personal experience, not evidence).
Gnomes have always suffered in comparison to other races for the reasons stated above, not the least of which is that certain things attributable to gnomes of legend were allocated to other races. This is especially true of attributes from legends in which gnome was but a synonym for dwarf, elf, goblin, or other mythological creature. Sometimes all of those names were interchangable. You may respond that obviously gnomes had no real identity then. That's not so- that just means that none of those races had a discernable identity until the game designers allocated some abilities to Elves, some to Dwarves, some to Goblins, etc., leaving gnomes with little to call their own...and that little bit got whittled away in successive revisions. (In a sense, its analogous to the Corellan/Grummsh myth...)
Bottom line - the designers of each edition had a chance to design cool gnomes and routinely failed. The 4Ed designers had their chance and instead chucked them in favor of new races.