Kala unlike the other supports does not fall under the category of defensive or offensive thus makes her one of a kind. Kala is what I like to call a passive support.
What I mean by this is Hank shields, that’s his main thing, shield and orbital whenever it’s off cooldown, that makes him defensive; Bucket has AoD, he does heavy damage and primarily focuses the Monster over teammates, this makes him offensive; Cabot has a damage booster, he has to focus on both Hunter and Monster alike but primarily Monster since he must know when to amp and when not to as well as where to use his dust tag to help his team find the Monster; this makes him offensive; Sunny has a shield drone and jetpack booster, she almost always worries about her teammates making her heavily defensive.
Kala has a very different kit, Kala has elements of Cabot with the armor reducer and also elements of Bucket too (I’ll get to that later) but also has a tool that can be used extremely offensively or defensively. She doesn’t deal too much damage but she doesn’t help the defensive capabilities of the team either. Her teleporters are what make her incredibly unique as they can be used as a trapping tool, an assault tool, an ambush tool, an escape tool, a repositioning tool, etcetera.
She doesn’t do well on her own but she doesn’t act like other supports. The team is what makes or breaks Kala more so than any other support as unlike other Supports, to be played effectively Hunters must keep an eye on yet another element of battle.
Similar to Bucket and knowing where his turrets are so you can lead a Monster into heavy damage, with Kala you must always know where her portals are, where you’ll end up if you go through, who you might screw over if you force the 15 second cooldown by using it, who may need it more, where the Monster is, etcetera. If you do not keep tabs of all situations of it then you might get medic killed or you might accidentally teleport 200 meters away from the dome because you didn’t notice that Kala hadn’t replaced the second pad yet.
Kala is very passive, she helps the team in a lot more ways than one, she helps Trapper gain map coverage, she helps Medics escape scary situations, she helps Assaults get into those same hairy situations, etcetera. She can be played offensively but then shift to be defensive at a moment’s notice unlike other Supports. She requires a lot environmental awareness, much more than other Supports. This is what makes or breaks her in a game and that is why she doesn’t appear as effective as other Supports. People just aren’t used to that extra level of awareness that they must have in order to succeed.
This sums up my feelings and views on Kala as I don’t agree with the “Defensive” or “Offensive” mindsets on Kala as presented in @TrickshotMcgee’s post (Not saying it’s wrong or anything)