Ethereum's ecosystem cannot optimize for running dapps because the true value of its token is dynamically determined byt he blockchain network, for whatever value the minimum of its token provides. For eg, a gas is worth whatever the world wants to pay for it to use it as a unit of calculation on the world computer. To accurately measure the effort spent by the network to ensure the unit value of its token , we need a DMMS algorithm(as described in the sidechains paper) & which is nothing but a proof-of-work blockchain.
Each primitive operation needs its own blockchain for its value to be determined accurately. When multiple token are implemented over a single blockchain, for eg colored/custom coins, it cannot accurately measure the value of a unit.
In case of functional language, one could perhaps imagine a lisp blockchain with paul graham's 7 primitives implemented as an opcode (stack based interpretor is irrelevant), which would be turing complete but will suffer from the problem of determining the true value of each opcode; the cheapest one will always be abused as evident on ethereum (suicide function's cheapness was spammed).
It's kind of weird to compare Bitcoin to Ethereum. They are both blockchain-based, but they're in completely different categories. It's like comparing shares in Exxon to an account of Wells Fargo. Sure, you can use them both as a unit of accounting but they're not really the same.
Ethereum is an autonomous app hosting corporation. Bitcoin is an autonomous ledger hosting corporation. They will succeed in their respective markets based on demand for ledgers and apps, the utility of decentralization in those two spaces, and their usability relative to competitors.
Ethers can be used as a currency, but so can oil, corn, and Beenie Babies. Bitcoin's purpose is currency, and the ecosystem around it is optimized for that purpose.
Ethereum's purpose is executing computational contracts, and the ecosystem is optimizing for that. You can compare the two the way you compare boats and fish, but anyone who puts them in the same category without caveat is really missing the bigger picture.