Serious performance issues after migrating SQL SERVER 2016 on a windows platform from windows Server 2012 to 2019

We migrated sql server 2016 from windows 2012 to windows 2019 and we had very bad perforamnce on queries.. we updated stats with full scan, rebuildd indexes after migration.. looked at Mx dop cost of threshold etc all loked good from our side. but no improvement and asked windows and network team to look what are rubnning new in 2019 vs 2012 and they found out that They have identified one potential issue that may be causing the performance drop between Server 2012 and Server 2019. We've noticed that Server 2019 does not properly disable Windows Defender when FireEye is installed, which may be causing additional resource contention from having two malware scanning platforms installed and running concurrently. Uninstalled windows defernder reboot and BOOM all queries are running as before in old production system