The most current philosophical arguments for the existence of God?

Semantic content is precisely the issue that is in view. The point that Feser is illustrating is that no particular triangle can determinately represent the concept triangle as opposed to something more specific (such as triangle with these angles and side lengths) or more general (such as 2-d geometric figure), and all material triangles have features which are not part of, and in some cases actually at odds with, the concept of triangularity.