Compositing makes old computer laggy, because Xorg causes a high CPU usage. To check if compositing is on run

gsettings list-recursively | grep -i compositing

To disable compositing, run

gsettings set org.mate.Marco.general compositing-manager false

If you want to enable compositing, run

gsettings set org.mate.Marco.general compositing-manager true

More settings from: https://wiki.archlinux.org/title/MATE