This is a BE idiom so I don't use it myself, but as I understand it, it really mean 'Different strokes for different folks' or 'Tastes differ' or 'To each his own.' Those are about different people choosing different things, but this saying is about finding the right person or thing for a particular purpose.
A question in one of the forums above was a good example. Someone said, I want to buy a medium-price computer, what kind should I get? The answer was, Horses for courses, meaning, it depends what you want to use it for.
Or I could imagine soccer or basketball fans discussing why a certain player was brought in late in the game, saying, Well, it's horses for courses. He always makes a lot of fouls and errors, but he's also good at raising the energy level and creating scoring opportunities, so right now he's the best choice.
So I would think it might be better to say (as a literal translation) 'Was/Wer für das Eine geeignet ist, muss für das Andere noch lange nicht geeignet sein.'
Maybe in the morning, the BE speakers could confirm or correct that, and possibly suggest a few better examples.