It wasn't a loophole, it was the law. Aereo were following Copyright law and previous case law as exactly as possible. The Supreme Court changed that law in their ruling, because they felt it went against the 'spirit' of the law.

Isn't doing something that is legal but goes against the spirit of the law by definition exploiting a loophole?

Edit: now that I think about it, there is room for a distinction between areas where case law hasn't ventured and exploitable holes in areas that case law has explored. But I'm interested in hearing if there's a more formal definition.

It's only a loophole in the sense that the true spirit of the law is "you can't do anything that upsets powerful media creation or distribution companies."

That is exactly, precisely the spirit of the (all) law. Except instead of $media creation or distribution companies, we should probably say $entities. And maybe add an addendum that says "unless you are a larger, more powerful entity."

Does anyone still believe that "loopholes" are a real thing? You know who writes the laws don't you?

This loophole was a result of the original law being passed in the 1970s. I'm not sure conspiracy theories will stretch to time travel.

The law was written in the 1970s to apply to some entities in some ways, to other entities in other ways, and not at all to yet other entities. This was intentional on the part of those who wrote it. No theories are required to observe such a basic fact.

Unless maybe your point is that there weren't any lobbyists in the 1970s, that there were but they weren't corrupt like now, or that any political era you didn't hear about from CNN was some golden age? That's cute.