Why couldn't there be more classes?

I mean, it's good where it stands now. But it would be fun and more diverse with like 1 or 2 more classes.
Why did the devs choose for 3 classes instead?

 

Defense, attack and support.
It's already a mayhem to balance so if you add two more classes...

 

But how does Overwatch for example manage to balance 20+ classes?

 

These aren't really the same kind of game.
Watch fun ctf, there are many new classes and they're unbalanced a lot.

 

Because they are done by modders. Also I think 5 classes shouldn't be too hard to balance. I played on Ninja CTF today and it seemed balanced.

 

I've always wanted a Medic class like in TF2 But that would never work.

 

More classes would work, but it'd require more effort as well as a fairly drastic change in how the game is designed.

The classes in KAG don't share very many things with each other. In Overwatch (and most other competitive FPS games like Planetside 2, CS:GO, TF2, etc.), the classes share a similar structure, but they all have a unique trait that defines them. For example, medics can heal and sometimes buff or revive players, heavies move slower and deal more damage, lights move faster and have more mobility, engineers have support structures, etc.

In KAG, however, the classes are very different. Knights have no ranged attack of any kind. Archers have no melee attack. Builders barely have an attack at all. Knights and archers can't build anything. Knights and archers have separate methods of fast movement (sprinting in other games), while builders have none at all. Knights have cheap & ineffective mobility and combat based explosives along with expensive, effective structure based explosives, while archers have effective ranged explosives. Builders get all sorts of things, like drills, boulders, trampolines, tunneling, etc. Archers can climb trees. Knights can surf.

There are so many differences between the classes that more classes would have to be extremely creative to compare to the originals. Think of it like an RGB wheel you see in paint programs; there are a lot of murky colors, but the colors that will always stand out the most are red, green, and blue. No matter how you mix those three colors, the color you create will always stand out less.

In order to have more classes that actually get played, the current classes would need to be made a bit more generic, and all classes would have to be balanced against each other so that none of them are more powerful or detailed than another. This would be difficult for an indie team, as it requires a lot of effort.