The advantages that Bitcoin offers are already in other emerging alt coins. They even have better features in actuality. The only real advantage that Bitcoin has is its popularity since it is the first go-to coin for people who want to start with crypto.
I agree with you that Bitcoin attracts investors because it is the first digital currency. But its value is also an important factor that makes investors pay attention and invest in it. The high level of fluctuations that make investors more profitable is also an advantage for Bitcoin.