> 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).

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.