In the case of the 51% attack assuming the attacker performs malicious activities i.e. censorship, making changes to the protocol et cetera, the Hardfork which is produced, even with dominant chain-work (hash rate) doesn't necessarily make it the 'canonical' blockchain chain. There is no right or wrong blockchain, only one that people agree to use, but for this example, we will assume that the malicious 51% attacker produces a 'dirty' or the 'wrong' blockchain. Parties with aligned incentives can choose with collective effort to repoint their nodes to the clean version of the blockchain and ignore the version of the blockchain that has been subject to attack. Hence, even if a 51% of Bitcoin or Ethereum was practically possible (it isn't), it can be ignored.
"A rich human wishing to subvert a decentralised blockchain network has a massive incentive to do so, and the resources to achieve it" - Blatantly false. No one individual or entity have even close to the recourses to attack a decentralised blockchains like Bitcoin. Decentralised blockchain are Byzantine Fault Tolerant. You stated that Byzantine Fault Tolerance requires a multiple 'trust' sources - which is the purpose of distributed systems i.e. blockchains.
"You need a centralised authority". You describe that by trusting a blockchain you are assuming that at least 50% of the population aren't malicious. By trusting a centralised authority, you are trusting 1 of 1. A blockchain, it is N/2. Clearly more fault tolerant.
In "Why decentralised blockchains can't scale" you fail to talk about Layer 2 protocols that depend on the security of its Layer 1. I.e Zero-knowledge rollups can scale (and do) smart-contract decentralised blockchains by orders of magnitude without compromising on security. Bitcoin's lightning network currently facilities Bitcoin blockchain backed transaction that are instant and virtually free. You mention that sharding as compromising on security - read this: https://vitalik.ca/general/2021/04/07/sharding.html
"Condition 1: [NFTs] must be unmodifiable... Condition 1 isn't achieved because the technology isn't capable of it (as it's decentralised)" What? You just explained how with distributed Proof of Work consensus, it is extremely difficult to modify data on a blockchain.
That is the point: NFTs are new technology made real with blockchains... because they are a technology that can provide a proof of ownership of a digital asset that is unmodifiable.
The argument that blockchains are not secure and NFTs don't prove ownership are based off the false assumption that these attributes are involved with the user custody. Decentralised blockchains are secure and NFTs prove ownership, though to an address rather than personal identity like a bank or government proves ownership. Of course this means that individuals must learn how to properly custody their own crypto assets, but does not mean that the blockchain itself of NFTs aren't secure/don't prove ownership.
The environment argument has been debunked time and time again. "a single Bitcoin transaction uses more electricity (1810 kWh) than one million Visa transactions". You do address the rebuttal with “NFTs don’t directly cause emissions” and label it as a misnomer. The analogy you provide is nonsensical. You previous talked about in your article how power is used by miners to secure blockchains by Proof of Work, it is not a product of directly processing transaction (including NFTs). In your analogy, the factories machines are proportional to the amount of coal power the factory consumes, the same is not true for blockchains. The number of transactions (including NFTs) on a blockchain do not effect the amount of energy consumed by miners securing that blockchain. If NFTs didn't exist, Ethereum would no less consume energy.
Most of the Bitcoin mining is NOT located in China. The ban in May-June caused a great migration of coal consuming hashrate to renewables consuming hashrate in the unites States and Canada. Those percentages are not updated).
Not only does Bitcoin and Ethereum replace many archaic systems that consume way more energy and paper than them, but most of the energy is renewable and most importantly SPARE energy not being used by households. A lot of the energy consumed by Bitcoin is cheap since the energy produces is in surplus and cannot be stored, so miners make use of that are are incentivised to do so. Their presence also allows for more predicable and flexible business operations for energy produces and are mandated to not consume essential energy needed for households and industry etc.
https://www.coindesk.com/business/2021/03/05/the-frustrating-maddening-all-consuming-bitcoin-energy-debate/https://hbr.org/2021/05/how-much-energy-does-bitcoin-actually-consume
It is easy to call NFT's a speculative bubble fuelled by the greater fool theory that have no intrinsic value. Firstly, what is wrong with that? NFT players may be speculating on art NFTs by gaining exposure to the futures use cases of NFTs besides from art. Clearly people are finding value by using NFTs for identity, or being part of communities. And what about gaming? NFTs are a huge part of the metaverse and crypto gaming, where NFTs have uses beyond for looking cool.
Of course some small market capitalisation assets can be manipulated by large players or celebrities, but if you think market manipulation is a problem in crypto currencies, learn about how the stock and real estate markets work.
"Impossible to regulate transactions"
Untrue.
Bitcoin's UTXO model makes it difficult but not impossible to track one's transactions. Ethereum's account based model makes it relatively easily to track one's transactions - especially with the use of on and off-ramp regulation:
"Coinbase or Binance don’t require you to give your personal details or hand over control of your crypto wallet"
They do.
"Imagine being such an unstable and unregulated market that default rates are higher than on loans with 5000% interest rates."
This makes no sense to compare DeFi default rates with legacy finance default rates: Typical bank loans you are borrowing money you don't have - they are undercollateralized. In DeFi, all loans are overcollateralized, meaning that the lender is not subject to default risk.
