Mmm, crossed wires; I'll try to be a bit clearer.
I'm making two points here, that might be getting conflated and, thus, contributing to the confusion.
1) The clamour for the Tinker class is almost exclusively community driven.
2) The Tinker fantasy is largely taken care of by the Engineering profession.
The first point is the expression of players, while the second is the expression of developers. This is one of those occasions where the players and the developers potentially don't view something the same way, and the developers will always win when those two sets of desires clash. For example: Legion's class fantasy sold a particular fantasy for each spec, that was designated by the class designers. The community, who in many cases had a different vision, played almost no part in that design.
The community, as it often does, took what it got and either liked it or lumped it.
My view is that the developers likely feel like they're accounting for much of the Tinker class fantasy via the profession of Engineering. If players argue that such an approach isn't fulfilling that fantasy, then the developers are likely going to try and treat it via Engineering. This is assuming that they even agree that there's an issue in the first place, which is by no means guaranteed.
The conclusion I'm drawing is that the game doesn't need another class, the fantasy described is already catered for (strongly or weakly, depending on your view), and the in-game evidence seems to point in that direction.
Your mileage may vary.