You don't "have to" do several exercises for a muscle group, one exercise per day can work well for sure. For example one biomechanics guy claimed you can't really bias different parts of the triceps much so just pick one exercise. Or do dips and hit the pecs and front delts at the same time. According to Jones you only needed dips for full tricep development. And curl grip pulldowns for biceps. I don't know if I fully agree but you don't need all the different angles IMO. After stagnating loading-wise switch exercise, but not too soon or you'll never go anywhere much IMO. Once progress gets difficult any performance increase is more likely to result in more muscle. First weeks of progress are neural mostly. IMHO.
