Apps take a long time to start. Why?

I’m on Silverblue, running GNOME. Most of my apps are Flatpaks, but I find that even the apps which aren’t (e.g. Nautilus) often take 3–10 seconds to start. This is significantly slower than typical app startup on Windows. More to the point, it’s not much faster than what I got out of my previous computers, and I’m on a fairly speedy laptop with a good SSD and gobs of RAM, so I’m surprised everything takes so long. Is there anything I could do to speed it up?