Here's a sample I created with CodeSandbox on making a Responsive AreaChart component using svg & cubic bezier.
Based on solution proposed in this Medium Article: https://medium.com/@francoisromain/smooth-a-svg-path-with-cubic-bezier-curves-e37b49d46c74
Also Available on Sandbox: https://codesandbox.io/s/react-area-chart-vv9fy