But to me, I am fully in 3D. I am literally an extradimensional being to the bacteria. And I am so far above it (no pun intended) I am incomprehensible to anything that lives on that 2D slide.
Even if I assume the bacteria has some really good teachers and can build stuff (they actually do, they make biofilms that are pretty complex "superstructures"), the kind of thing they can do in their limited plane of existence is nothing compared to what a human can.
So while I don't believe anything that was released so far points conclusively to real aliens, I don't find the concept of extradimensional beings too far fetch.