In addition to @phw's explanations, this are the suggested steps to do in such "Consistency cases" using «MusicBrainz Picard» and the Musicbrainz website:
What I don't get is that even though my song file has the Title, Album Name, Artist, etc. (most of the essentials), Picard STILL can't find and put the song with the correct album.
This includes doing a "manual" Track/Album search, the correct Album WILL NOT be listed in the Search Results, and also the correct album IS in their database, for example if you check the website, or you search another song with the same Album, it might find it then.
And yes, I've changed all kinds of settings trying to get the correct Albums to show up etc.
I've had to use MANY 100's of wrong Albums/song data cause it just wouldn't find the actual album the song came from.
Oh, and I also don't get that when the file has the above essential tags, "Lookup" won't find anything, I have to use Scan for EVERY file almost. That's like "backward". Shouldn't we be using "Lookup" as the primary method when tags have the basic info already? I mean, audio analysis should just be for those things we can't find, the occasional issue or rare file.
You should ask this questions in the Picard forum: