The aim of the publishers was never to create an uncrackable game. But to delay crack releases enough so the game could sell. A game sells best the first weeks.
It doesn't matter if it's cracked 2 months later. Some games like Unreal were very tough to reverse engineer. Bad luck: the disk format was "warpable"/copiable in nibble mode. So there weren't cracks but the game could be copied as is and worked.
And some bad cracks were released too (because of the competition between teams). I remember getting bad cracks of some games, and ended up buying them
A good crack is 100% tested, maybe with infinite lives, to play through the end. Levelskip is cool but sometimes no good, because some protections made some levels uncompletable (Leander, Killing Game Show...). With levelskip you don't notice that.