There already was a time when Steam managed to free people from need to use funny pieces of plastic in their lifes... They've done that with CDs, they can do it again with Cards.
Yeah, that was when Steam freed the users from actually owning any game and instead gave the users limited licenses for using games. I am looking forward to the day when they shutdown and everybody realizes this.
Steam shutting down and taking your library with it really doesn't change much except you lose that nice delivery platform with good integrations (achievements, workshop mods, multiplayer integration, automatic updates) for games you're active in. For the 90% you were never going to touch again it wouldn't be noticeable, outside the annoying reminder you were never able to resell them. The other 10% just reverts back to "pirate it" which is about here on my scale:
"find that legal physical copy to play with" < "pirate it" < "click button on Steam"