This is also happening to me. It happens due to modified steam dll files, it is a simple anti-piracy tactic that the developer, SuperKu, used in Pogostuck.
why did you delete it? just get goldberg emulator and replace necessary files like steam_api.dll and steam_api64.dll and go into the ini fle you deleted and replace name igggames with something else . (edit i see why you deleted it now but don't do that)
I am unsure of how to fix this at the moment.
Edit: For anyone having this problem, removing the valve.ini configuration file from the game folder fixes it.
Don't bother telling me to delete valve.ini (the fix for a previous version), that file literally doesn't exist in the latest version you uploaded.
just get goldberg emulator and replace necessary files like steam_api.dll and steam_api64.dll and go into the ini fle you deleted and replace name igggames with something else .
(edit i see why you deleted it now but don't do that)
dont deny it the first time when you saw the title this came to your mind xD
I tried the Pogostuck 1.8k file but won't open :(
Please help