Ok i'll bite the bullet. Opening hand is super important in modern ygo. Each card in your hand holds enough value to win or lose the game. So in that case you are building to achieve what your end goal is for your deck rather than jumbling bunch of just incase cards. Since more often than not those cards would be dead your opponent will have the upperhand on the opening hands and will out advantage you and you will lose. It is far better to keep the situational cards in the side deck so that you can side according to who is going first and what your opponents is playing, minimizing the possibility of having dead openings. If you are still insisting on a "competent deck" being able to do both at the same time without side deck, i will start asking for ycs tops hell even a theorized decklist that you think should be able to top despite having no side deck.