If I come up with a much better way of doing something that is relatively easy to reimplement, there's no great incentive to come up with those ideas then.
I'm not suggesting that the current patent system works well, but you are in danger of throwing the baby out with the bathwater.
The incentive is in delivering first. When the free market saturates and profits are razor thin due to extreme competition, first movers always get the rewards of innovation
Counter: Netscape vs Internet Explorer. Netscape had a year lead, but it's hard to compete when Microsoft decided to bundle IE for 'free'.
If profit margins are razor thin, the Apples and Amazons and Microsofts of the world can happily copy an idea and hold their breath far longer than a smaller competitor can.
I'm not suggesting that the current patent system works well, but you are in danger of throwing the baby out with the bathwater.