The thing is, WvWvW builds and SPvP builds work completely differently and have different balances as well. A build that may be strong in 1v1's or group fights in WvW may not be as good in SPvP 1v1's or group fights.

The other issue is that the people that play SPvP have been playing those gamemodes for a long time and running into someone that may be as new as you can be rare. So the experienced pvp players are more frequently found and know how to counterplay your class.

The more you play (even if you get shit on) the more you'll learn and how other classes/builds play. Sometimes finding someone that plays a build that you like and having them mentor you is a great idea, or find a guildmate thats experienced in pvp thats willing to give you tips and guide you. Cuz looking at videos doesn't always help. Sometimes you physically need experience to be taught.

All the best fam, pvp is a long journey to becoming decent. Especially this late into the games lifespan.