‘Relevant’ is the word that can be used to describe ‘useful’ information on the internet. Because ‘usefulness’ is in the ‘eye of the beholder’. ‘Timely’ is also a related word because it indicates that the seeker can find the information needed ‘in a timely manner’.
Any attempt to categorise information into ‘useful’ or ‘not useful’ per se, would involve ‘one group of people who know they are right’ imposing their views on... everyone else. It isn’t possible to do that. This has been tried many times in history and has resulted in witch trials, book burnings, and the holocaust.
The authorities told people ‘what to believe’ during communism.
The idea of ‘useful information’ is based on ‘judgement’ without accepting that there are ‘points of view’.
Even activities such as ‘marking information as good and correct’ are entirely subjective. And can result for example in the ignorant ‘many’ marking a true piece of information as false while an Oxford Don, who knows the ‘true answer’ scratches his head in disbelief.
So one could say that there is ‘no such thing’ as inherently good or useful information. Nor is there a word for that. The usefulness of information is subjective and ‘in the eye of the beholder’. Discernment allows us to choose what to believe - or to choose - what is right for us personally to believe - in that moment.
In an expression form, on finding the perfect piece of information, one could say ‘that really hit the spot!’ Or ‘that was just what I needed to know!’ or ‘that information really met my needs’.