Ethereum was a GREAT idea, but not-so-great implementation.
Many voices have risen concerns about the code quality.
Then there were hacks, not necessarily in Ethereum, still, maybe a better design could have avoided that (I'm not certain though, since it's impossible to have flexibility and stability/safety well together).
Then there were the bad politics that have split ETH and ETC.
I still wait for the better competitor to rise, still, they are way behind...