No, only performing crunches is not going to get you a toned core. Well-sculpted abs are determined by two factors- the amount of time you exercise and the type of diet you follow. Only performing exercise and binge eating unhealthy food won’t help.
Secondly, crunches might be one of the exercises that can help you get a strong core. So, if you are only performing this exercise then you are making a huge mistake.
If you aim to get well-carved abs then you must work on your abs from different angles. You can do it either by including variations of crunches or other exercises that engage the maximum muscles of the mid-section of your body.