I don't think that this claim is true. Those "Bitcoin experts" cannot impose major changes to the Bitcoin blockchain, since there's no consensus around their proposals.
I agree they can't do anything unless there is a consensus in the marketplace--i.e. a consensus among those who would maintain the average current price of BTC.
The point here it make is the inverse: with this consensus,
they can do anything.
And keep in mind that while Bitcoin is technically a democracy (a democracy requiring a
majority sentiment, not a
unanimous sentiment I might add), in reality it operates more like an oligarchy: since people are motivated by their BTC price, big players and holders can force lesser holders to go along with them lest they be holding a worthless coin.
They could hardfork the blockchain and create their own version of Bitcoin, but they cannot change the 21 million limit or "freeze" anyone's coins.
Again, they make changes to the Bitcoin core codebase all of the time. With consensus (see above), you can do any of that.
I don't mind the coins in Satoshi's wallet to get burned, since he most likely would never use them, but this should be discussed among the community and a consensus must be achieved beforehand. The "quantum threat" is still a theory and I do believe that the blockchain could become quantum resistant without the developers having to "freeze" anyone's wallets and coins.
I'm sure it would be discussed among the largest holders of BTC and the largest distributors (CoinBase, Binance, Robinhood, the ETFs, etc.), but one place it would most certainly NOT be discussed is
right here. I'm pretty sure we don't matter

.