I love casual Smash Bros as much as the next guy, but some of it is not fair when the entire focus of competitive play is your skill with the fighter alone. Some final smashes are just flat out better than others (Daisy, Snake, Zelda), assist trophies and Pokeballs can be utter bull**** (Tiki, Rathalos, Keldeo), a lot of stage layouts can encourage running away, cheap walk off kills, or interfering obstacles (Palutena's Temple's size, any walk-off stage, and obstacles like the Flying Men or Yellow Devil).
The entire point of competitive play is to knock out as much randomness and unbalanced mechanics as possible for the purpose of making it... competitive. It's like football. You can play it any way you want with friends, but the NFL has their own rules dedicated to it.