When you "state the obvious", it's a truism

• From wikipedia: A truism is a claim that is so obvious or self-evident as to be hardly worth mentioning.

A self-evident statement is a Platitude

When you "state the obvious", it's a truism

• From wikipedia: A truism is a claim that is so obvious or self-evident as to be hardly worth mentioning.

In some cases, a "self-evident statement" may be a platitude (or less approriate in the question context, a "cliché").

• From wikipedia: A platitude is a trite, meaningless, or prosaic statement, generally directed at quelling social, emotional, or cognitive unease. The word derives from plat, French word for "flat." Platitudes are geared towards presenting a shallow, unifying wisdom over a difficult topic. However, they are too overused and general to be anything more than undirected statements with ultimately little meaningful contribution towards a solution.