The price of Bitcoin fluctuates by 10 to 20% in a day, which is very risky or frustrating.
This is not true. A 10 to 20% fluctuation a day will make bitcoin too unstable to invest in. Even within a week, Bitcoin doesn't do 20%. A 10% decrease in bitcoin based on the current price will take bitcoin to about $96k, which we haven't seen I a very long time. We usually see a 1-3% fluctuation in bitcoin daily, not 10-20%.
Not to mention, it should be noted that its short-term volatility can cause our asset value to drop suddenly and can cause us some trouble if we want to spend.
I think it's an established fact that Bitcoin is best as a long-term investment. It is almost certain that in the long term, Bitcoin will give you profit, but in the short term, it is not so certain.
A lot of other assets also don't guarantee profit in the short term. Gold, Silver, stock, real estate, all don't guarantee profit in the short-term, so it's not that different from Bitcoin in this aspect.