If you don't do this, the overwhelming tendency is that the graph traversal algorithm snakes its way through your program and is a huge pain to change and reaso

If you don't do this, the overwhelming tendency is that the graph traversal algorithm snakes its way through your program and is a huge pain to change and reason about. Indeed. There is a balance to be found. Over-engineering and using the wrong abstractions hurts. Working with an “organic design” that has no useful separation of concerns, or forever reimplementing the basic data structures and algorithms of whatever domain you’re working in instead of doing creative work that is going to solve your real problem, also hurts. Too far towards either extreme and development progress slows to a crawl while quality plummets. I wish we had a bit less emphasis in the industry on always using the latest shiny tools and a bit more on learning good fundamentals like data structures, algorithms and design patterns. Of course abstractions sometimes need to evolve as requirements do, but identifying which abstractions are helpful at present or when an existing abstraction isn’t helping any more and should be removed or replaced is absolutely a skill that can be developed with knowledge and experience, and it pays huge dividends to those who cultivate it.