Why does my pc load games up so slow?

I have an older computer, it's about 4 years old now, and when I boot up games like Fortnite or even when loading up Discord, it drags. With Fortnite, it takes a long time to load up, and when I play with a friend, they will load into the match fine, but I won't load it until the bus kicks everyone out. I don't have a lot of things installed, so I know it's not something storage-related, and I've been keeping up with driver updates.