A lot of people wonder why the kindred cardtype in Magic can’t be a supertype or why it’s even necessary in the first place and I’ll explain that here!
It was decided once upon a time that subtypes belong to specific card types. Like “aura” is an enchantment subtype, “elephant” is a creature subtype and so on. And the game rules is a super stickler about this point. It’s something it really insists on.
Now, could this decision change? Yes. With strange aeons even foundational rules can die.
That’s actually one of many reasons why Wizards better never hire me as a rules manager because I’d spend so much time trying to undo this “subtypes belong to specific card types” rule because I think that rule is so dumb. I’d just have a trait list and I’d make it more than just one line too. (Similar to how Netrunner does it.)
But dumb as it is, it does have a silver lining: because of this rule, if the game sees a card that’s “enchantment creature — aura licid” it can know that the “licid” part belongs to the “creature” part, and the “aura” part belongs to the “enchantment” part.
Now, if that li’l silver lining makes the restriction worth it (especially as they’re moving away from subtypes having rules baggage, like how it’s snot the “aura” part that makes enchantments stick to stuff, it’s the “attach” part that does that)? I’m not sure. But it is what it is and that’s why it’s there.
By now that’s also something that digital relies on It knows that a “destroy all goblins” it only needs to look at creatures and kindreds.
However, while subtypes can’t be mixed and matched, two card types can share subset typesets as long as they share all of them. Instants and sorceries share all the same subtypes, which is why both instants and sorceries can be arcane.
And that’s why kindred: it’s a card type that share the subtype typeset with creature without sharing creatures other rules baggage like being permanents.
If this could be done with any other marker, like a supertype, it wouldn’t need to be a supertype either. In that world it could be a keyword even or a li’l icon or whatever. And maybe that is possible with Magic rule 101. That’s the paradox of this: if this could be a supertype, it would not need to by a supertype. That’s a mindmelting sentence so let me try again:
If the card could just say “This sorcery can have creature subtypes even though it’s not a creature”, it could do that through card text or a keyword granting that ability.
If the card could not just say that, it couldn’t do that with a supertype either.
Now, one advantage for our très cray future rules manager unraveling all this stuff to prefer making it a supertype instead of other kinds of markers like keywords or icons would be that exitisg kindred cards would still look right. “Kindred Sorcery — Goblin” Would look the same, visually and typographically I mean, as it it does now when it’s a card type. But that’s really the only advantage in the supertype camp.
The reasons Wizards don’t like it is that it doesn’t make sense to only use it some of the time. Like if a goblin sorcery can be gobliny, why isn’t a fireball spell fiery or a counterspell wizardly or a heal spell clericy or an ice spell icy? They’d have to put that stuff on all the cards all the time (which I’d think would be pretty cool actually, hence why I’d want to move to a multi-line trait system) and they don’t like putting stuff on there that the current environment doesn’t even refer to. So either you always have kindred on everything or you never do it, was their thinking, and that’s why they stopped using it.
It used to be called “tribal”. Maybe if there hadn’t been genocide against the tribes we wouldn’t have to be so eggshells about this stuff but now listening to them is the least we can do and “tribal” was an awful name for it in the first place. Card types have changed names before (creatures used to be called summon spells in some zones) so that’s not new.