Wechat keeps capturing my screen

Wechat is a third party application. If it had really been deleted, there is no way it would be capturing your screen.

I am not familiar with the application, but maybe it installs some background add-ons, in which case it is not enough to just drag the application to the trash. If it came with an uninstaller, you should use it. Maybe now a simple solution is to actually install the application and then use the uninstaller.

If you don't want to go that way, please post a full Etrecheck report. We may be able to glean from the report which background agents or daemons are still installed and so be able to direct you on how to remove them.

Look in Settings>Security & Privacy > Privacy > Screen Recording and also Settings>Security & Privacy > Privacy > Camera to see if Wechat is listed and remove it