Yes, at a time of decline like this, we must hold a stable coin so that our assets do not go down so badly that the USDT is currently rising well, is this investment possible? Yes, it's better to hold USDT than other coins.
But investing on a popular coin might help you to gain income in the future. Investing it on bitcoin as of now since the value of it is now cheaper than before and gain profit into it when the price of it rises up again. That is a simple buy low and sell high principle. Traders are into this one and they are not afraid to take risk even though the value of the coin is cheap.