The original printing of the 5e PHB had some rather unflattering descriptions of half-orcs, and under the heading "The Mark of Gruumsh" said, among other things: "Half-orcs are not evil by nature, but evil does lurk within them, whether they embrace it or rebel against it."
There was also this gem in the section on alignment: "The evil deities who created other races, though, made those races to serve them. Those races have strong inborn tendencies that match the nature of their gods. Most orcs share the violent, savage nature of the orc god, Gruumsh, and are thus inclined toward evil. Even if an orc chooses a good alignment, it struggles against its innate tendencies for its entire life. (Even half-orcs feel the lingering pull of the god's influence.)"
This got changed at some point before 5.5e – I'm not sure when, to be honest. But it's pretty clear that the original intent of the 5e rules was that orcs, goblins, and so on were if not strictly speaking
always evil, as close to it as doesn't matter, due to the influence of their creator gods.