If bitcoin is made as an alternative currency to the Fiat currency from your point of view, then there is a limitation in it which is also contrary to your point. Like if I want to buy shirt in my locality I can't use bitcoin to buy the clothes so I have to sell the bitcoin first before I can use the Fiat money to pay for shirt. And that is a big limitation of bitcoin. Bitcoin is an alternative coin, and that means bitcoin did not come to take over Fiat currency but it came to support it and make it stronger. The only thing is that bitcoin removed the third party control. Everyone control their funds. So if you have 1 BTC for 10 years, your 1 BTC is still intact. But in Fiat banks it you have 1 million, it will reduce within 1 year because their service maintenance fees, electronic maintenance levy, card maintenance levy, SMS levy, USSD levy and Internet Maintenance levy etc. Because of all these levies and fees, BTC comes the best of all.
The sad thing about the current situation is that people do not really keep their coins, they give it to others and that creates all these trouble. The latest one was once again an exchange, FTX, where people trusted their coins to them and they lost it and now people do not have their funds, while bitcoin itself is decentralized and gives you freedom, if you give up that freedom and give others your money, then you should not be shocked to learn that they used your money for bad stuff and lost it.
This is why bitcoin is not just a tech, but it is an idea and the tech part may have been understood but the idea behind it is still not fully comprehended.
Exchanges are not like banks, although both are centralized, you cannot compare the safety of the two. Leaving money on an exchange is too risky but with a bank, our money is much safer.
Bitcoin is decentralized, it gives us freedom and self-determination to protect our assets but putting all your assets in bitcoin does not guarantee our security. Given bitcoin's volatility, it's still a good investment, but not a reliable place to store money. If you convert all your money to bitcoins at the beginning of the year your asset value will drop more than 75% right now, but if you deposit it in the bank, you will lose only a few % of its value. Both have their own benefits, so why not combine but compare and choose only one when we can use both?