Contrary to general opinion the pectorals (pecs) are not a large muscle group. They can be classified as a small muscle group, just like the biceps. However many has distorted our views when it comes to muscles. Several sources are claiming that pecs and biceps are the biggest and most important muscle groups in the entire body. However this is not at all true.
The standard flat bench is also highly overrated for actual pectorals growth. It’s more of an ego lift and should be left for the middle or end of the routine- there are far better movements that will provide a much better outcome. OF course the flat bench should not be neglected. However, a common misunderstanding in the bodybuilding community about the pectorals is that there are multiple pectorals- inner, outer, upper, and lower pecs. Anatomically this is not true: you should be thinking of your pec as one large muscle broken down into the above mentioned quadrants (inner, outer, upper, lower).