I’m not a fan of exercises and don’t do them regularly. When playing violin pieces, I occasionally play the scale corresponding to a specific key for tuning the notes. The focus needs to be on the repertoire pieces which are more exciting.
The age thing is partly to do with people’s perception on learning. Some people assumed they need to pay for a teacher, practice for years, learn to a high level before they get anything out of music. Starting young would be the only way to get somewhere. Like learning a foreign language we learn to speak early and would speak at every level. Around Christmas many people would play a few seasonal tunes. Even easy arrangements are nice.
Some of my teacher’s students are retired adults. Besides age we all have 1 thing in common: lots of free time. Grandpa & grandma enjoy playing for the grandkids as listening to them play. Music is a shared experience. A few weeks ago I was sitting at a piano in a senior home playing a Bach piece out of a suite that is barely 1 1/2 min. A lady stopped by in her wheelchair chair. I don’t play the most challenging pieces but enjoy the experience very much.
We can enjoy music playing at any level. A teacher is helpful but the need for one can be over exaggerated. Yesterday a friend came for dinner. He calls himself an amateur pianist. Without formal lessons, can’t read sheet music he can play some American show tunes by ear convincingly.
The main thing is not to compare yourself with other people and enjoy the music.