Not especially exclusive to crypto casinos, but casinos in general. Ideas that make it big elsewhere are copycated all the time. I guess you'll know this only when you try all those shady online casinos that are out there, especially in China or Philippines!
Personally I think copycats are in every industry. If you have a mobile app and you don't want to pay, and are forced to watch ads, then you know what I mean. Thousands of ads all looking the same as each other.
Same as going to Google Store search 1 app, see 100 copies.
This happens everywhere, if a product which is innovative is released and people are buying it in just a few days hundreds of cheap copies appear on the market, but this is stifling innovation as those people need to pay all the research costs and when they finally have a product they can sell it is immediately copied and they are not paid any royalties either, so I think this is the reason why no one is taking any risks as it simply makes no sense for them to take them.