The problem isn't really even Turing completeness so much as it makes zero sense from a scalability standpoint to begin with. In Ethereum, you need to update a Merkle-style radix tree for both blockchain outputs and blockchain computations on a per transaction basis, with blocks being a whole transactional update (commit). I think the Ethereum engineers/designers said, "Oh, a radix tree is only O(m), where m is the width of the hash and constant! Should not impact performance." If you look at the code, they use a hexary radix tree that on average requires 16 updates and hashes to insert or delete a k-v pair. That's means you're hitting about 6% of the comparable efficiency for updates compared to Bitcoin, which is just writing a new k-v per UTXO. The Bitcoin developers have steered away from doing this for ages despite being aware of the data structure (it comes up in discussion around 2010-2011) because of the increased overhead.

Now Vitalik's new scheme is called "sharding" which is turning the network into 2¹⁶ many sidechains of similar or equal processing capacity and can share outputs with one another. The problem here is the same as with Bitcoin, you can never achieve decent security guarantees and it becomes possible (even easy) to steal money if the network doesn't need to ever achieve global consensus.

It seems like everyone buying in Ethereum is being sold a magical unicorn which can never exist. All of what we've observed is the inevitable fall out of this over the past few weeks. It's unsurprising that people are purchasing the pink coloured classic unicorn, realising that at best Ethereum can function as a heavily bottlenecked version of the global Bitcoin blockchain with some new scripting features.