This is true, although those who have invested in bitcoin in recent years will not be able to receive the same level of return as early investors. But its return will also be significantly greater if we compare bitcoin with other businesses or investments. Bitcoin remains the most promising investment in terms of returns.
I absolutely agree that someone shouldn't firmly rely on Bitcoin as your primary source of income, but rather should view it as a side hustles. In all seriousness, it is extremely risky due to Bitcoin's nature of volatility; the price is not always stable; the price can drop to any level, even though it can also move up to any level, and that is why some experts in the cryptocurrency industry always advise not to invest in bitcoin what someone cannot afford to lose. Therefore, it is better to have several sources of income and pursue bitcoin trading or investment as a side hustles because doing so will significantly aid in your investment's growth and enable you to realize profitable returns.
Whether you are investing or trading bitcoin, it will never give you a steady income. So it would be foolish to consider bitcoin as the main source of income and depend entirely on it. No matter how profitable bitcoin is, but since it is very volatile and we never know when the profits will come, so always treat it as a side business rather than the main one.