Designing and Development are respectively two different fields. Both fields have different tasks to perform. Both designer and developer belong from the different planets and do not speak the same language. In simpler words, they both have different job roles and differ in nature as well. There is an effective way to classify the two positions separately if roles are clearly defined for each position for a web design and development project.
Infographic Source: https://www.arpatech.com/blog/designers-venus-developers-mars/