As soon as I gave up playing Unorthodox Chess Openings in Fide Rated Chess Tournaments, I started to gain elo points and I lost less games. Hard to admit but it happened.
Still I believe that some UCOs, such as 1.g4 or 1.e4 Nh6 are FULLY playable but they are impractical. I mean that they require an enormous amount of attention & energy to keep a balanced position...and as soon as you (the UCO player) make a slightly inferior move, the position risks to precipitate rather quickly...
For instance, this is not the case of the Colle System where you can obtain decent middlegame positions without risking too much.
As I am getting older, I get tired more easily and I do not feel comfortable to invest so much energy in the opening, although it is so much fun to play UCOs!
BUT in my opinion UCOs are FANTASTIC in rapid, blitz & bullet games/tournaments where the reduced time control & suprise effect may support the UCO choice.
Please consider that this is my opinion & experience...NOT the absolute truth.