I think some more healthy competition against Core would be welcome
You are confusing "healthy" (ie positive-sum) competition among consensus-critical blockchains with unhealthy zero/negative-sum contention within a single consensus-critical blockchain.
Altcoins are Bitcoin's healthy competition. If Bitcoin isn't competitive we'll use Litecoin, Primecoin, and Monero instead.
Classic and other XT-like governance coup attempts are declarations of a war that only one side can win.
I think "healthy" competition can come from both inside and outside of the Bitcoin ecosystem. Internal competition becomes problematic when productive discussion and collaboration devolves into mudslinging, which it too often does.