If an engineer is operating at their very best, most time would be spent in designing.
Rolling back a few years in time, I used to work on a platform where a team of engineers took 2 whole months to just design the schema of a particular object. It was shot down by the CTO, they went back to the drawing board and came up with another design a month later. The office hours were spent debating the schema and trying to break the workflow and coming up with potential issues that the schema can cause. When the design was finally agreed upon, it took 4 days to write code. The system is so stable right now and their support ticket numbers are in single digits. During my initial days there, we used to jump into code without thinking a lot like morons. Our support ticket numbers used to be in triple digits back then.
So, taking time in designing things is absolutely vital. Spend 80% of your time designing and 20% of your time writing code.