I feel like this is the issue with calling most software development a form of engineering. That term has been mostly adopted for prestige or to make it seem much more established than it really is. Certainly in some limited domains, yes, it is engineering and what you said applies to it, for example if you're developing software that controls systems whose failure could result in loss of life then you must be accredited as a Professional Engineer to do that work. But the vast majority of software development does not adhere to engineering principles in the way that civil, mechanical, electrical or chemical engineering does.

For most software projects including web development or CRUD applications, there is no known best methodology to solve problems. Despite how passionate some people are about extreme programming vs. pair programming vs. TDD vs. this vs. that, there is surprisingly little empirical evidence that one methodology is actually better than another. We do what we do out of imitation rather than out of solid and well researched engineering principles.