Again, you don't have to play Arena games to become a guru.
Currently gurus are selected by the number of games (and again, this is not limited to Arena mode) they played during last 30 days.
If you want to share your opinion on Catan, you should write on Catan subforum or player group rather than here.
And as others said, the vote not solely depends on the game's depth, but on the waiting time too as the player pool is smaller than normal mode.
In fact there are many games with 2 player Arena setting to keep it running even if the recommended player number is 3+.
Dunno whether this applies on Catan too though.