In a story like "The Day After the Day the Martians Came" sure, the purpose of the aliens (Martians in that case) is purely to tell us about us.
But you don't really need aliens for that, there are several Black Mirror stories which do roughly the same perspective trick, particularly "Men Against Fire". Aliens offer an opportunity to explore something quite different and it's always disappointing to see them used as something less interesting.
It's like FTL. FTL is actually exactly equivalent to time travel, and so it's disappointing, though commonplace to see SF which decides to do FTL but no time travel (or indeed vice versa though that's less common)..
I like Culture novels just fine, I like Greg Egan's Amalgam setting (with aliens who are basically just us again, although a bit less obviously so than a Star Trek alien) just fine, but, in both cases I'm a little disappointed. If your aliens aren't even as weird as the Octopus is (and we have no idea what the fuck is going on with an Octopus) then you're not really trying are you?
Aliens are hardly ever more than a tool to get a perspective. To look at humans, societies, structures etc. They are also stories _about us_.