Zelda and Roy mains can be really good but when they are put against the really good S Tier they will loose. Not that I am suggesting to ditch them because maining lower Tier characters will get you respect.
During friendlies my Roy was actually beating people's pocket spacies but my Sheik was loosing to them. They probably just didn't know the matchup. I would say my Sheik improved but I still need to work on mobility.
Also this advice helped me a lot: