Why can't I mine it?
Why can't I create a cold wallet?
Why is XRP listed on coinmarketcap if it is not a public crypto?
Is there a website that lists and compares only cryptocurrency that can be mined by the public?
Because of it's all premined. But you can buy it. (Actually what's the difference between buying a miner plus buying electricity then getting coins and buying and getting coins ? Cloud mining is even more similar. Almost identical .)
Google is your friend. You can create a cold wallet: https://forum.ripple.com/viewtopic.php?f=19&t=8733
Because of it's a publicly available and as such it's a "public crypto".
As coinpr0n said try using the filters on coinmarketcap.