Guild Wars 2

The Engineer has some big problems with their unique class mechanics.
The main class defining traits are the kits and turrets. The toolbelt I would say is only there as a side result of these. The developers, for whatever reason, decided to make the class defining kits and turrets normal utilities. The toolbelt mostly just compensates for the loss of a utility slot to these by adding an additional skill.
They likely work for normal utilities as well just to avoid pressuring players into choosing ONLY kits and turrets.

The big problem with this is that you are not required to have kits or turrets. Because they’re a choice they can’t be superior to other options, but by refusing to be superior you also have no clear incentive to pick up these CLASS DEFINING MECHANICS.
But whether you pick them or not, you suffer penalties in exchange, like not being able to swap to a secondary weapon and only having a choice of three weapon types, one of which can only go in the off-hand and therefore only has two associated skills.
I can see someone arguing that the four extra toolbelt skills compensate for the lack of weapon skills, but consider this; other classes get extra skills in this area AND a secondary weapon plus greater weapon variety.

So here is my proposal.
Make the toolbelt skills customizable much like normal utility slots. Two or three of the slots are reserved for either a kit or a turret, and the other one or two allow a choice of any of the four available toolbelt skills based on your utilities.
Kits and turrets would then ONLY be able to go on the toolbelt.
When a kit or turret is currently active, the toolbelt slot gets replaced with the associated current toolbelt skill, like Bandage for the Med Kit.

This would ensure that all Engineers have some combination of kits or turrets, and therefore access to their class defining traits. It would also prevent them from wasting utility slots on these just like every other class is able.
These mechanics, and the class as a whole, would also be much easier to balance since they are not only assured to have them, but they are also limited from being able to load up every single slot with them.