不人気街道一直線
I found this expression on few Japanese sites (social mostly, so it seems like some slang?), but what does it mean? I guess it means 'unpopular', but that's not enough for me if I see so many other elements to this.
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Sign up to join this community~街道【かいどう】
is used metaphorically in the same way as "Road to (success, victory, becoming an actor, etc)". And ~街道【かいどう】一直線【いっちょくせん】
is a set phrase which means "marching down the road to ~".
不人気街道一直線 itself is not a set phrase, but a kind of ironical usage of this phrase. It roughly means "falling straight down to the abyss of unpopularity."