What do I need to upgrade?

Currently running these current specs (from the top of my head, not specific)

GTX 780ti I5 Processor (3.2GHz) 8GB RAM

I currently struggle to run games such as PUBG, lowest settings and get poor FPS, poor visual performance, common crashes etc, Is this normal for this kind of build? Something tells me my GPU might just be dead, it's 3 years old.