With my limited understanding on bitcoin and bitcoin transactions, I think there are 2 barriers for it to et bigger adoption as means of day-to-day transactions worldwide.
- Block size: The block size is capped and limit the maximum of transactions per block. The max transaction counts per block is not a fix number as it depends on total size of those transactions in a single block.
- Fee structure: Now, the rate of fee per vbyte (in satoshi) is decided by senders. They are components of fee race. The more people want to make transactions, the more hurry people who accept to take higher fees. At the ends, fee will automatically to be lifted up and only small senders (send small amount of bitcoin) will be charge a big percent of fee per total amount sent out.

- More adoption for Bech32 address on centralized exchanges (that I hope will increase in 2021).
- Increase the blocksize more, scale it up
- Second layer solution as Lightning network.
- Change the algorithm for fee structure (is it possible per protocol?): I think this point is very important and if it can be done, it would be a big boost for bitcoin adoption. Fee will be stable in satoshi/vbyte, for instance: X USD vbyte and the more vbyte a transaction has, the more fee with be paid.

Only the fee in USD will be changed with bitcoin price in USD. Is it possible per Bitcoin protocol?

The biggest problem I face is not being able to use Bitcoin for our day to day transactions, not because of high Bitcoin transaction fees
or the volatile price of Bitcoin. But because the government in my country prohibits using Bitcoin for payments, so Bitcoin in my country is
legalized only as a digital asset.

Sometimes I am jealous to see people living in countries where the government does not prohibit using Bitcoin for financial transactions.
I agree that for now the fact is that Bitcoin is not ready to be used for day to day transactions. There are still many obstacles that must be
found the best solution first before using Bitcoin for day to day transactions.

I did not see it happen because bitcoin has already experiencng down trend and probably will going to continue for more due to the fact that many users now are earning with bitcoin after they sell everything they had. I myself had already selling even I had a little bit of btc holdings to get the chance to earn more while bitcoin market is high. Today, bitcoin market would probably go down depending on the bicoiner.

I first got into BTC when it was around $400, and by the time I used it for my first "day-to-day" it was still around $600. It's today around 60 times that value and still hasn't stopped being useful for that purpose. You see, not every Bitcoiner thinks like you expect. Virtually all of my income now as a freelancer is paid in BTC. Sure, I hold as much as I can, but I see value in spending and using it. And a lot of others do as well.

Lightning is also a thing, by the way, and in places like Arnhem in the Netherlands, where Bitcoin merchants have already started adopting Lightning, people continue to use it to pay easily for smaller transactions. I easily see a future of $100k BTC where $1 transactions of 1000 satoshi are easily settled over Layer 2. $1 million BTC? 50 cents (50 satoshi payments) are just as easily done.

Yes, countries will definitely create a central bank currency (CBDC). 

Organizations registered in these countries (as well as citizens of these countries) will use this currency as a means of payment.  However, the question arises ...

How to determine the allowable volume of CBDC money supply (for each country)?  For example, one country will issue a large number of CBDCs and another country will issue a small amount of CBDCs. 

How to convert one currency to another?  Countries do not exist in isolation.  They interact with each other.  This is why a world reserve currency is needed.  In theory, it could have been gold. 

However, how to check how much gold is in the hands of the state?  This test is not easy. 

Bitcoin is another matter.  Thanks to the transparent blockchain, every country can easily prove that it controls its bitcoins.

It was evident for years. Bitcoin transaction fees are too high to use it for making small purchases. Another problem is that sometimes you have to wait to long to get two confirmations.  

People need to understand that under current scenario, Bitcoin is more useful as an investment asset rather than as a mode of payment. Anyway, who want to make payments in BTC, when it has appreciated by close to 300% during the last four months? For grocery shopping and all, what you need to do is to convert some of your BTC to gift cards. You can use these gift cards for shopping. Grocery items are priced in fiat currency anyway, and therefore it makes hardly any difference.

With the amount needed for Bitcoin transaction to be successful, for sure not all can afford to use Bitcoin on a daily basis as a mode of payment for transaction fees are incredibly getting higher as time passes by. It is more likely Bitcoin is good as an investment asset rather than being of a payment option. Yes, Bitcoin is good for payment option as well but it seems that due to high transaction fees, people are more likely be treating Bitcoin to be used for investment opportunities. The reality is just that people would prefer exerting Bitcoin to be conducted as investment assets to gain profit instead of using it for small amount purchases considering you will be spending transaction fees on that and confirmation is taking long to be done as well. Having Bitcoin to serve as transactions method is good but now on a daily basis.

i think what he means is that we shouldnt spend our btc because btc value can grow more in value and we can regret it someday but i also like your point that we will only spend useful things that can help us but this also works on almost any currency and payment system we have .
 money is earned in hardwork so we should spend it wisely  .
 groceries and gas is i can say something that is valueable because we need food to live and we need gas to run the car for buying groceries or for other transporting purposes  . gas and food value can grow in price overtime too