Don't forget that Peercoin and Datacoin (two very notorious Alts) have their technology partially integrated in nearly every Bitcoin 2.0 project (even those built on top of Bitcoin).
The two Bitcoin core devs I have met so far have had more or less the same opinion. To an extent I can sympathise with them being hard on the security and cryptographic side and the destructive part of having too many blockchains. I believe this is a necessary evil, since a lot of code and financial based experimentation is still required to find the golden balance and this experimentation cannot be done directly on the Bitcoin blockchain, nor in Bitcoin Testnet.