Dembele being able to combine with Coutinho and Alba helped him a lot. On the RW he'll be isolated and have Roberto and Rakitic who both don't have 1/10th of the vision Alba and Coutinho possesses to combine with.
Moreover you have to return to a 4-4-2 formation which alters Dembele and Coutinho's positions and hinders their creative ability. It's a way more rigid system than the one we're playing right now.
And if we play a 4-3-3 still then it's still an issue as Suarez will have to play LW/LF which he's simply not capable of doing anymore. Messi lately has been going wide to the RW at times to receive the ball, more so than before which opens up the field. We should keep it that way.
The reason we're underwhelming or playing boring football is because of the manager and not because Dembele plays LW or that the right side is empty. The right side would be empty regardless of what we do unless Rakitic becomes more pro-active and we get a proper attacking RB.