I think ERC-404 will be adopted for a few distinct purposes in the future: for example 1000 identical NFTs, worth an outfit in GameFi, or 1000 identical NFTs representing ownership Music album, which is about to be released.
Anyway I will wait for the widespread adoption of ERC-404 and its uses from new projects 
Yes, you are right, erc404 will eliminate the uniqueness of the NFT, NFT rare and NFT common the price will be the same, this is currently a problem and is being developed, this includes the shortcomings of erc404.
ERC404, to be honest, I just got this information, I still need to investigate this problem further.
After I read the article you provided here, the author said that this token is still not official so it is still very risky to transact, but to test the feasibility test, you should use this, if the fees offered are cheaper, there is no harm in continuing with this token.
Hopefully in the future more projects will use this token and it will be mass adopted by new projects
This is just one of the benefits provided by the erc404 network, so we don't have to wait long to sell the NFTs we have, if we usually have to wait for people to buy them.
For the time being it's only on the zkSync Era network but it's still being tested.
When Ethereum was still POW, the price of Ethereum was probably under 500 USD and the fee was definitely cheap because calculating from decimal 1 Ethereum was equivalent to 500 USD.
After Ethereum changes to POS, the price of Ethereum may be above 1700 USD or more and the fees will definitely be expensive because the fee is calculated from 1 Ethereum equal 1700 USD.
Unfortunately, Ethereum's current position is V2.0, where the price of Ethereum is already expensive, above 2000 USD and there are more and more L2 projects, NFTs, ERC404 standard tokens, etc.
If later the price of Ethereum is 10,000 USD and the position is still POS with V2.0 and the fee for one transaction is around 50 USD, would you still say that currently the transaction fee of 2 USD is expensive??
I once found an article that discussed transaction fees on the Ethereum network almost the same as your opinion and it is not wrong, but in my opinion the ETH transaction fee cannot be ascertained only by the price of Ethereum as you say why, because Ethereum transaction fees are flexible can be high and low depending on the density of transactions on the network.
I once made a transaction on the L2 Ethereum network for a fee of $1 at that time the Ethereum price was $2k, this is for transactions such as sending coins and claiming NFTs, it's different if you do a bridge, if the bridge depends on the platform.
So what do you mean is that if I sell this ERC404 NFT token, I can sell it directly on the DEX without having to open an NFT website like Opensea?
Yes, you are absolutely right so we don't have to go to the NFT market and wait for someone to buy our NFTs, this is one of the advantages of Erc404.
Have you invested in this ERC404 standard token?
If you have invested or bought it, what type of ERC404 token is it?
I haven't made any investments in this erc404 developer, ERC standard tokens have not undergone the vetting process common to all ERC standard tokens. Such as the submission of an improvement proposal (EIP). and the request for comments (ERC) stage,Since it has not undergone such a process and has not been audited, the project may have many weaknesses that can be exploited by irresponsible parties.