I built a demo app to show my problem in another thread.
Just extract the rar to juce\extras and then build and run. It has a slider in a window. When you drag the slider it repaint the main component with simple lines and colors. When dragging it you can check the CPU usage. It’s about 40% for me.
Copy the project to the same position of a old juce library (before low level graphics change). Rebuild the project and run. Drag the slider and watch the CPU, it’s about 15% for me.