The LingQ metrics are meaningless for me, because of the way I am using LingQ.
I am primarily using LingQ because it has graded materials with audios and transcripts. For a new lesson, I will read it online, listen to the audio online, and then download the audio and the transcript. After that, I do all of my listening offline, and after I have listened enough times so that it is easy to understand what I am listening to, then I login to LingQ and mark the lesson as complete.
When I read the lesson online, I never create any LingQs, and so all of the words become “known words” when I am done. This works for me – “known words” are the words I have seen before. After listening to an audio 30 times or more, I am familiar with any new words and feel like I “know” them, at least in that context. And if a word is truly important, I will continue to encounter it in future readings and audios, and “know” it more deeply.
Another reason why I do not pay any attention to the LingQ metrics is that I have been learning Italian for two years before I joined LingQ, and I have other sources of materials for reading and listening.
I do not need metrics, because I can tell when I am improving. And with all of the graded materials available on LingQ, I could test myself at the various grades to see where I am currently at.
Having said all of this, I think that LingQ is a great resource for me, and I wish I had found it a lot sooner. I plan to continue using it, until I reach an Advanced level, which is probably still a long ways off for me. And even if the features I am using did not require a paid subscription, I would subscribe anyway because I want to support LingQ because it is helping me and so many others.
And if the LingQ metrics, challenges, etc help to motivate people in their language learning, then I think that is great. But if the metrics don’t work for you, then set your own goals and milestones.