There is a way to buy bitcoin for cash, but this method is not very convenient for me, because for this I will have to overpay significantly more fees.

But I doubt that the banking system will just collapse at once, or I doubt that the cryptocurrency will separate from the banking system, and frankly I don’t see much need for this. Over time, people themselves should understand the advantage of bitcoin and this will even out the balance in the right direction.

Currently there are many countries where Bitcoins aren’t legal. Those nation’s banks are forced to forbid any transactions related to cryptocurrencies. But still many people of those nations are doing trading on a daily basis. How are they doing this? They are doing the transactions through P2P deals. Here you trade the Bitcoins and cash with other peer rather than directly to the bank. In this manner the bank can also find out what commodity you purchased through that transaction. P2P is the best way to buy Bitcoins and that too by remaining anonymous.

Aside from P2P, You can use money remittances to purchased Bitcoin. In our country, there’s an app called coins.ph that let you cash in fiat to their system through the use of money remittances services then let you convert it on Bitcoin without the use of banks as middleman for your transaction.

Banks is inevitable to use when we are talking about fiat. We might see some alternative but we still need banks in the future once we are dealing with huge amount. The only time we don’t need bank is when Bitcoin becomes a legal tender since we can purchase goods using it directly.

Purchasing bitcoin without involving a bank will be hard, for instance here in my country if you say, you don't do a bank and hold cash all the time, you get someone to buy the bitcoin from and you gave the person the cash. The person needs to save the money or else the money will be idle instead of saved and converting it back to bitcoin. This is just a scenario which hard for you to have face-to-face conversations with your buyer or seller

This is possible in our country using Peer to peer transactions. But I don't know if it's legal in our law since their minimum is too high, and I'm unsure how safe it is. So If you want to do this, ensure you will negotiate with someone you know or an individual your trustee will recommend. I have no other option since I'm still using the bank to buy and sell my cryptocurrency. What's the purpose of cutting ties with banks? I'm just using the bank to lessen the hassle and risk of meeting someone.

Actually, we can still not be able to cut from banks 100% fully. We may try using P2P transaction, but we must ensure that it is really secure.So we can trust the people to buy or sell the Bitcoin. We need to research that the P2P is guaranteed as well. But here, exactly, I personallly still cannot get it easily because I am using exchanges for transactions and I uses bank account as the manner

Peer to peer is the possible way we all can buy bitcoin without the help any bank,  and interestingly, the p2p market have very much advanced from what it used to be some few years back, p2p has gone digital, no longer analogy like it used to be.

Several big exchanges now offer p2p market to their users, providing a safe place, for user to buy and sell bitcoin safely without the involvement of any bank.

That's something done 9 years ago on this space where there are less users and less exchange.
But for enable to use or get fiat, getting regulated on the country where the company is based, it's a different story.
I think it will happen only when all or most services where necessities can get accept bitcoin or crypto as payments.

The sad part about your response is that buying p2p can get you in trouble. Assuming your Bitcoins increase in price and you want to cash out after a certain holding period, financial authorities will ask you where you got those Bitcoins from. If you didn't document precisely who sold them to you, and if you don't make sure that the data provided is true, you might get a problem because you can't prove the origin of funds and the date of the transaction, which could be relevant for tax calculation purposes depending on the country you are living in. P2P trades can bring their own set of problems to the table. There might be countries where it is possible and no problem at all, but I know countries where it could turn into an issue as soon as you want to turn it into cash. If you do that with a p2p trade again, you can still be stuck because you can't easily buy a house and tell financial authorities that you got lucky. Again, it all depends on where you are living.