I know the main reason for you on this site is because of this problem “You cannot delete a plugin while it is active on the main site”. It occurs when you try to delete an active plugin and is very simple to fix. I will lead you to fix this problem go through it properly.
As you can see I was trying to delete WP Disabled and faced a similar problem.
Accordingly, if you want to remove this plugin you just need to purge all cache. To do that you will need to have the W3 Total Cache plugin installed.
Now, after installing the plugin if you have not installed it activate it and proceed further.
You will see the performance option on the top bar in the dashboard. Click on the button and a dropdown will appear.
After this select purge cache and clear all cache reserved by the plugin.
Further, try re-deleting the plugin. Now it is successfully removed.