The currency would crash and everyone move to a different currency if the wallets were cracked. It would then becomine a premine which destroys the reputation of the network and no one would use it.

I cant imagine that would happen due to the amount large scale investors in charge of quantum computing and the currency itself.

I'll help you, enter this into ChatGPT: Please explain what "more insecure way" means for a non native speaker. What I wrote does not match the content of your question.

No, pressuring or pushing and forcing are not the same things. The difference is literally part of the definition of the words. If you are forced to do something one way, then you can't do it another way. If you are pressured or pushed to modify your behavior, you can still do things differently. Very different and important distinction especially when you talk about security.

Weak and useless FUD. Nobody is going to start using your shitcoin with or without quantum computers cracking wallets, get over it.

Not quite perse.
Here you can see where there was a flaw in random number generator for ECDSA and some addresses were affected
https://bitcointalk.org/index.php?topic=581411.0

If the address wasn't reused or remained unspent, then the movement of their funds wouldn't had been possible.

Unspent address protected by SHA256 and RIPEMD160(which hide their public key) and ECDSA (which secures the private key)

Reused address( the one after spending) have their public key exposed so their security relies solely on ECDSA which is susceptible to future quantum attack and vulnerability in ecdsa generation. 

I believe we talking about P2pkH.

Yes, of course. And they should also warn about many other things, for example that a partially signed transaction, which is signed with something else than SIGHASH_ALL, can be modified by third parties.

Even if secp256k1 will be fully broken, it will be still possible to use OP_CHECKSIG in a safe way, as long as SHA-256 will still be safe, and Proof of Work will be enforced properly. Some example: https://bitcointalk.org/index.php?topic=5551080.0

If someone will break secp256k1, without breaking SHA-256, then that person could clear puzzles from 60 to 40, but going further will still require gradually breaking SHA-256.

Yes, we are. But P2TR can be spend by key, or by TapScript. Spending by key can be blocked in the future, if needed, and then, quantum-safe paths will be executed inside TapScript. As long as SHA-256 is strong, this approach would work. It is not yet decided, if quantum-safe addresses will be deployed inside TapScript, or if a new address type will be made.

Making coins unspendable can be done as a soft-fork. Even invalidating all existing UTXOs is still a soft-fork, see here: https://petertodd.org/2016/forced-soft-forks#radical-changes

Because it allows N-of-N multisig, which looks in exactly the same way, as a single user, spending things with a single signature.

They could use HD wallets, and use a tree of public keys, to derive next addresses. Then, key derivation path could contain user ID, transaction ID, and other unique data. In this way, when each deposit will be done on a different address, they won't be broken all at once, as long as public keys, which are used to derive them, will remain hidden.

No, Proof of Work can be used, too. But I guess not everyone wants to be a miner, and using optional Proof of Work to limit double-spending ability of some third parties also comes with a cost of grinding transaction hashes, which is huge, if there are many inputs and outputs.

Well, if your coins are not KYCed, but you make a transaction on a chain, where everyone else went through KYC, then everyone knows, where you are. Which means, that by reusing your own address, you make everyone else's coins less private, because if you have a new key, then it introduces deniability, and then, people are no longer sure, which coins are owned by whom. By reusing addresses, coins owned by the same party can be linked together.

It is all about not having all eggs in the same basket. Which simply means not having a single re-used address, but some HD wallet, where compromising a single key would compromise a single deposit, from a single user, and not everything, sent by everybody.

Of course, funds can be accumulated into bigger denominations, if needed. But in practice, quite often, they don't have to be. You don't need a huge transaction, collecting hundreds of satoshis into whole coins, and then another wave of transactions, splitting them back. If someone deposited 100k sats, and someone else requested a withdrawal of 99k sats, then that coin can be moved directly, with 1k sats in fees. Which means, that coins can be accumulated when needed, and a given coin doesn't have to be merged from 100k sats into 100 BTCs, and then splitted back into 99k sats.

For example, it is mentioned here: https://groups.google.com/g/bitcoindev/c/ydE5u5C0xVc

In general, if P2PK will be blocked on consensus level, or if it will be turned into non-standard, then exactly the same things can be done to Taproot outputs, which are spent by public key. Today, you can attach 64-byte Schnorr signature, and if it matches a given Taproot address, then it is considered valid. In the future, it can be rejected, and then, only spending by TapScript will be possible.

It is in my signature, and I also made a separate topic about only that: https://bitcointalk.org/index.php?topic=5551080.0

To sum it up quickly: I think there is no need to fully invalidate OP_CHECKSIG as an opcode, because it can be used beyond just "<pubkey> OP_CHECKSIG", and can still be used for other purposes, for example to require a given amount of Proof of Work, to spend a given UTXO.