The chair probably needs replacement if adjustments do not make it comfortable. A worn-out chair shows flattened cushioning in places. It shows loose joints. It shows a creaky frame. When lumbar support does not maintain the normal curvature for the lumbar spine, the spine may stiffen with the development of low back pain.
If you can fidget in your chair, you have to lean forward or put cushions in your lower back area, and you have to get up and move around every few hours, your chair may not be ergonomic.