Imagine you have a small modeling agency. You have like 10 girls, most of them hover around 6/10 in looks department, you send them to do ads for small companies, assist small events and so on. One day you see an application - 10/10 girl with tons of experience. Way above what you're doing here. What is the correct move? You should reject her application - having ten 6/10 girls and one 10/10 girl will create lots of drama, which will offset any gains from having her on board. If you want your agency to improve, you should hire a 7/10, maybe 8/10.

Exactly the same principle applies with engineers. If you have a team of idiots and you hire one of top programmers, you'll create friction in the team.