I can not stress enough that consistency is the number one factor to the success for any target archer. I have witnessed kids and adults alike with horrible archery form that continue to be somewhat successful because they are very consistent.
However, as an athlete starts to explore the depth of their abilities in a sport, there are things they will need change and improve, for various reasons, to achieve the next level, no matter who you are.
In 2003 Tiger Woods, after his second consecutive Masters and Fourth consecutive Player of the Year award announced he needed to make adjustments to his swing to help reduce wear and tear on his surgically repaired knee. Arguably the greatest golfer in history needed to make changes as part of his development and therefore so will you.
Archery and Golf have a lot of similarities; standing a great distance away you send a projectile through the air towards a small target with the goal to put it into the middle. The main similarity is you only compete against yourself; no one is stopping you from being your best. It is as much mental as physical.
The only constant is change… Isaac Asimov
In your early development as an archer, you can work on a couple of things at the same time however as you develop you need to focus. There are many different approaches to consistent good form and therefore there will always be a certain amount of trail and error involved. Once an archer reaches each level of development they will experiment and need to try various things to find out what works for them. The higher the level of development, the smaller the level of change, and it is often more difficult to implement. Therefore it is important to work on only one thing at a time so that you are not confusing which change is working to your benefit and which is not.
In my own development, I struggle with staying focused on just one thing at a time which is the double edged sword of wanting to achieve perfection. So focus on one thing at a time because you do not want to be second guessing whether it is one change or another that are affecting your shots.