Good question. There are a few main things that make so many cryptos different from Bitcoin.

1. Network Influence: many of the coins out there (ether, doge, solona, etc.) have a small group of developers that can change the protocol in dramatic ways whenever they want. For example, in Ethereum, there is a set of developers that have regularly changed the chain history and consencous rules in dramatic ways to reverse hacks and push certain agendas. None of this is possible with Bitcoin, as there is no central group of devs.

2. ICOs: many coins have an initial coin offering that gives a large portion of the coins to an initial set of VC funders, giving them great control over the network. This did not happen with Bitcoin.

3. Developer subsidies: there are a lot of coins that give devs, marketers, etc. a built in on chain reward. This gives an inside group of people an income stream that no one else is even open to accessing, meaning the network does not possess equality of permission. Again, Bitcoin does not have this trait.