> Instead, think of replacements that have caused something to basically just disappear.
Okay, SSH and Telnet. SSH is not as simple to use as Telnet. Windows users have to download a client, even in 2016. Server key changes cause warnings. People are often using encrypted key pairs instead of password authentication.
These (network admins who care about BGP) are sophisticated users. A secure version of BGP is not going to be as simple for them to use. It's just not happening that way, that's the way it always goes with security. More security makes the product more difficult to use, and a secure version of BGP is going to be more difficult to use.
Yes, you can find examples of simpler products that have replaced more complicated products, but that's rather poor support for the idea that replacements must be simpler or they won't be accepted. We're replacing magnetic strips with chip & pin for our credit cards, which are more complicated for everyone. Unencrypted HTTP may never completely die out, but HTTPS is everywhere and is only getting more common.
Or if you want simpler examples, think of the smart phone replacing the flip phone (less battery life, more complicated, more expensive) or the MP3 player replacing the cassette player (more expensive, more complicated, you have to get a computer and rip your CDs or buy digital music online). Or think of locks replacing simple latches on doors, now you need to carry a house key with you.
Or if you want examples more similar to BGP, think about spanning tree protocol. It's simple and it gets the job done. It's also completely dead in the modern data center, replaced by things like the far more sophisticated software defined networking. BGP is headed for the same fate.