Those aren't equivalent comparisons. The issues with Ethereum have all been with regards to implementations of applications on top of the ETH layer - parity bug and DAO hack being the two biggest. Neither was due to mistakes in the underlying Ethereum protocol, both had to do with something that someone made using Ethereum.

If I make a vulnerable website it's not nginx/Django/Postgres's fault.

The reason Ethereum hasn't taken over the dominant position yet probably has more to do with Bitcoin's superior brand penetration. Most Bitcoin holders that I know personally have very little actual understanding of how any of the crypto currencies work under the hood, so they follow the general sentiment of the community/press and do not invest based on technical merits.