Alternate Bitcoin?

What is to stop someone from creation a total copy of bitcoin.. thus diminishing it's value? Bitcoin is capped at 21 million coins.

But there is nothing stopping someone from creating say Bitcoin2.0... and startin over from scratch. And 3.0 and 4.0... and thus, the number of coins is infinity!

There's lots of crypt curencies and many attempt to fine tune the algorithm in some manner. But seems to me... copying bitcoin... is easy to do...

Alternate Bitcoin?
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