I'd say "both".
1st, you need to help them get the RCA on why this question, and what context (that isn't often brought up). Its often that framing the question in context elucidates the actual problem they are working on solving, and they are seeing a misfit in concepts with the solution you've gone over with them. This is one (of many) areas where being a senior (experienced) dev/manager/leader is so critical in developing the less senior folks.
2nd, curation of notes, experiences, techniques is absolutely critical for team capability growth. Capture the problems, explain the use case/back story, explain the problems in explicit detail, explain the thought processes around the solution, and the solution. Cut-n-paste examples help. I did this when I ran my company, and found that it was quite helpful to the team. And they followed the example, and documented their own efforts.
Please don't be snide or dismissive with the less experienced. One of the reasons I see many orgs hire older/senior folks is to provide a calming, thoughtful, intentional influence on other team members.
As others have pointed out here, you need to continuously grow, learn new skills, add new capability. This should be a given. I don't want to bring "lifers" (people who hide in a company, doing only one thing, never interested in developing). I want to bring curious, intelligent people, with capability, and experience. Or if lacking experience, then a strong attitude of wanting to get their hands dirty.
Age doesn't factor into this.