Frankly, you will not enjoy WoW class design. It’s fairly basic across the board and is honestly one of the weaker points the game has in comparison to other modern MMORPGs.
FFXIV beats it hands down no contest in this department. Across the board.
I always say I prefer WoW’s combat pacing, but prefer FFXIV’s class design.
Anyway, as a couple others have said, Feral Druid is a decent choice in terms of pure complexity (still not that complex, but can be in comparison to many other specs/classes), but it’s nothing like a Mechanist. It’s fully melee. And you’ll be shapeshifted and never see your actual character. And it’s often an underperforming spec outside of PvP despite the complexity.
So then in terms of theme/role, Hunter would be the best choice, but, again, as has been said, it’s one of the simplest classes, even with WoW having simplistic class design across the board. You could run a petless MM Hunter with guns instead of bows/crossbows, but if you’re looking for a super complex, tight rotation that scares people away because it’s hard to get right, this is literally one of the last specs I’d recommend.
So, for now, I guess I’d just recommend taking the time to create some Class Trials? They start you off at level 110, but the base mechanics of a class do not change between there and 120. You have to go through the little intro/training scenario before it lets you change your spec or go anywhere, but it only takes a few minutes.
Keep in mind the scenario only shows you the basics. You’ll finish it with like 4 or 5 buttons on your bar total. You can explore the rest afterward. Head to a city and hit the training dummies or whatever.
Also keep in mind that the class trials are given essentially leveling gear. They are not strong. Haste makes a fairly noticeable impact on combat pacing in WoW, as do procs, which are often affected by Crit. So think of these as a baseline that will get stronger and faster/smoother as you gear.