They work fine for input stages. You can get parts that are ”better”, but having them on hand is better than waiting 6 months or a year to get the “best” ones.
A42/92 are sometimes used too. They aren’t the best choice for input stage because of the lower gain, but can be used in places where 5551/5401 can’t. When you see someone using A42 input stages, one of three things is happening. 1) The voltage is too high for anything else, 2) The builder only wants to carry one universal TO-92 pair that will work anywhere and sometimes they need 200+ volts, or 3) They don’t know any better.
