What does QFT say about what exists?

You come across various existential statements in your quantum field theory texts, such as:

even matter itself is an excitation of a quantum field

and find that many authors seem to come short of attributing reality to, say, the physically meaningful quantities that remain invariant under gauge transforms. And it's usually ambiguous whether the objects of such theories are to be taken seriously only pragmatically, or if we're to understand them as constituting reality in some fundamental way.

So, assuming that QFT describes what exists, what exists according to QFT? Are there any texts that explicitly go over this?