Two problems with this. One, it was never actually stated in the show that this was the reason the angels were helpless against the leviathans, and unless it is in one of the next couple, this is just fan speculation.
Two, assuming it is correct, why does it only work on angels? They're also older than demons and ghosts and witches, but didn't/couldn't nullify them.
Castiel killed a vampire in Mommy Dearest, and once Eve was dealt with in the same episode, immediately decimated all of her remaining Jefferson Starships. Angels are clearly able to deal with most monsters, Eve was the exception (and apparently so are leviathans).
Though really, that thing with Eve being immune to Castiel's powers because she's older than him was just a hand wave to explain why he didn't just teleport in and shove the ashes down her throat before she could process what was going on. It's a bit depressing that we're having to use it to justify the leviathans now.
I don't think it's just a matter of being older (never bought that). I think being older gives them special insight in what to do to mess with their powers but just being older isn't the whole thing. We don't really know it doesn't work on demons just because Dick ALLOWED Crowley to leave is limo doesn't mean he couldn't have stopped him if he wanted to (just was no point in it).
Also it likely wouldn't work on ghostsbecausepresumablythey've never had to deal with them. Leviathanswere banished before humans were made so they would never have dealt with an actual ghost before and thus would have no idea how it works or how to defend from it.
Even so Bobby's attack too a lot of energy out of him so we was still dealing with a massive resistance but not a knowledgeable or skilled one.