I have a next js application where my mobile score for performance is 12. I use to have a decent score a few years back of around 65. I have upgraded from next js version 8 to 11. I have also updated my react to the latest version hoping that would improve my score a little bit but that hasn't happened to my surprise.
The worst hit is my LCP score please find the screenshot for the same below:-

My http://localhost/_next/static/chunks/pages/portal.js?ts=1629050439458 transfer size is 2,649.8 KiB attaching screenshot for the same below:-

When I had started using next js it was truly meant for production but lately, I feel I have missed out on some major updates due to which my performance has dropped drastically.