Tinkers are the most logical step for a new class in WoW. They are the only class that has no representation yet is a fundamental part of the lore of at least two races: Goblins and Gnomes.
Everything else at least has some representation. SOME. Necromancers could represent the idea of death themed undead summoning caster infinitely better than current death knights, but the rep is still somewhat there.
There is something admirable in all of Azeroths leaders that would make a player want to imitate them. Not perfectly, but it’s there.
You want to be like (classic) Thrall? Beseeching the elements and spirits for aid? You can be an orc shaman.
You want to be like Garrosh, Cairn, Muradin, Greymane, or Varian? Warriors are there for you.
You want to be like Anduin, Velen, Moria, or even something darker like Natalie Seline? Priests are there for you.
You want to be like Uther or Liadran? Paladins are there for you.
You want to be like Malfurion? Druids are there for you.
You want to be like Chen Stormstout? Monks are there for you.
Maybe you want to imitate the villainous leaders? You want to be like Gul’dan or Arthas? Warlocks and Death Knights are there for you.
You want to be like Sylvanas or Vol’jin? Hunters are there for both of them. Shamans and priest are there for Vol’jin. It’s not perfect, but multiple classes have been used to represent them at times.
But you, a loyal gnome or goblin? You want to imitate your leaders, Mekkatorque or Gazlowe? Nah you’re out of luck. No in-combat mechsuits. No excessive explosions of bombs and bullets. No cool in-class gadgets. No Tinker backpacks. Nothing you can play can represent them well.
Tinkers work. They work really well, and a hell of lot better than bards, which have no important representation in lore anywhere.
PS: Obligatory necromancer request: You want to be like Kel’thuzad? You’re also out of luck.