Opensubtitles became really frustrating to use once they began asking for a login and a password to download subtitles in VLC or Xbmc/kodi (basically every time you need to use the API). I always forgot about login details and in my opinion it wasn't needed at all for them except for profile tracking I guess. They forced people to register to get subtitles, they willingly forced people to increase their attack surfac…
This was actually optional, and always was. I think the issue was that they had made some changes in the backend, but the addons didn't update the code to accommodate. At least this was the case for Kodi. The opensubtitles addon has essentially become abandonware anyway. There are now third-party addons that provide the same functionality but without a login, and across different subtitle websites.