Depends what you mean by good.
If you want to play so well, you have a very low handicap, it will take a long time and a lot of practice. These days, unless you a naturally gifted sports person, you really need to start as young as possible. Golf is not about pure strength as many female golfers hit the ball further than most men and nearly as far as the best pro’s
Golf depends on two main attributes. Flexibility and timing.
This is why the sooner you start, the better. Young people generally have far greater body flexibility and the timing is easier as they show no fear of swinging through the arc to hit the ball. They will hit many wild shots, but usually, if they have a modicum of skill and dedication, will achieve a very good standard.
However, many people take up the game later in life, perhaps after children have left home, or they retire of just have more time on their hands. They can still get a great deal of enjoyment from the game but will still need to practice a lot.
Golf is all about attitude. The golf swing is a counterintuitive action, unlike any other sports movement and is not easy to master consistently. If it was we would all be playing like the pro’s.
If you dedicate sufficient time and invest in good quality clubs and take lessons, a lot more than you think, you should achieve a reasonably good standard.
I have played for many years and have reached a mid-handicap level. This is good enough for me to play reasonably consistently and enjoy my golf with players of a similar standard. However, there are members of all golf clubs who never seem to enjoy themselves, always moaning about the shots they played badly, rather than enjoying the shots they played well.
Is it hard to become a good golf player? It’s as hard as you want to make it.