They are not at all. Governments and financial institutions can lock funds, do 'hair cuts', as they did in the European financial crisis, and engage in other such shenanigans. They can debank or otherwise exclude people and companies from the payment system, or refuse them banking services at all.
But really, your statement says it all. This is what anti-Ethereum advocacy amounts to: advocating for the legacy financial system, and the one Satoshi Nakamoto specifically criticized, including in the Bitcoin white paper:
https://www.bitcoin.com/bitcoin.pdf
"Commerce on the Internet has come to rely almost exclusively on financial institutions serving as trusted third parties to process electronic payments. While the system works well enough for most transactions, it still suffers from the inherent weaknesses of the trust based model. Completely non-reversible transactions are not really possible, since financial institutions cannot avoid mediating disputes. The cost of mediation increases transaction costs, limiting the minimum practical transaction size and cutting off the possibility for small casual transactions, and there is a broader cost in the loss of ability to make non-reversible payments for nonreversible services. With the possibility of reversal, the need for trust spreads.
Merchants must be wary of their customers, hassling them for more information than they would otherwise need. A certain percentage of fraud is accepted as unavoidable. These costs and payment uncertainties can be avoided in person by using physical currency, but no mechanism exists to make payments over a communications channel without a trusted party. What is needed is an electronic payment system based on cryptographic proof instead of trust, allowing any two willing parties to transact directly with each other without the need for a trusted third party. "
>>Also DeFi apps are very illiquid and extremely complicated to use.
Uniswap had $10 billion in trading volume over the last week. That's in the same league as major exchanges like Bitfinex and Kraken. It's also extremely easy to use, with no sign-up/registration required, and a trade being possible with 3 clicks.