What was they thinking when they did variant dungeons and criterion

[Absimiliard]

This might come as a shock, but content doesn't disappear when it no longer has rewards for you to gain. It's still available to other players for the first time, it's still possible for other content to require it (such as relic).

This might come as a shock, but most players would prefer to be rewarded for their time when engaging in challenging content.