Yes in almost all casino games luck is crucial, it is made that way. On other games like sports betting or poker there is more skill and knowledge involved. So probably, unless person is seeing future, in casino games it is completely irrelevant if someone is following instincts or not, result will most probably be the same.
I consider instinct as way of decisioning based on your feelings. It’s really a big deal since we completely don’t know what will be the outcome but it’s a big help on when to stop gambling or not.
In blackjack, I follow my instinct and combined it with perfect card matrix strategy for my next move. There’s a lot of time when you need to decide on your own feelings which makes gambling challenging and fun.