RPG characters and creatures are created. To some extent, your class, feats, special abilities, and so forth represent things you trained, but also things you are naturally good at learning. In real life, we sometimes find we have different strengths and weaknesses, which sometimes align with what we want to be good at, and what we are willing to work towards, and sometimes not. But a character's life and outcomes and powers are always what we pick for them.
Part of the reason heavy multiclassing in unpopular is because it can look, at times, not organic. On the other hand, locking certain traits behind certain class choices or levels can also feel less than organic, if they seem like things that fit the character we have in mind.