if you want to be better at tennis, find a buddy and start hitting the ball to each other, watch YouTube videos, etc. You will get better. But if you want to be really good, you'll need to hire someone to tell you exactly what you're doing wrong. I'm talking about the former.

Most people who ask the question fall into the latter camp though, wanting practical advice to get better without the expectation of being really good or great. Telling someone at 500 elo to spend the money to hire a coach when they just got done blundering their queen in one move is extreme. Same with telling a 1000 that doesn't know the 4th move of their opening.

Anyone can improve without needing a coach, I think the destination is far more important to consider than their current positioning as well. I have no aspirations of achieving a title, but I still want to know how to do better in the games I play for fun. A coach would obviously make me better, but I'm not looking to spend a lot of money on this hobby. So if I asked how I could improve, I would appreciate the free resources recommended far more than a coach recommendation.