In my opinion stable coins are bad to invest.
I am agreed with you that stable coin is bad for invest because we cannot make much profit from it. if its price had not been stable then we can make good profit from it. you can use stable coin for holding your money for a short time when you think other crypto market tend to be dumping continuously.
Stable coins are not good if they are made investments because their prices are fixed and unchanged, sometimes there are people using stable coins for the purposes of securing their assets from deep price declines, with the existence of stable coins our assets become safe