Like mos people, I think that you have the power but just aren't putting it out to the pedals. Most of my rides, the Strava estimated power output is around 240, why..... I'm doing some work when I ride the bike.
It used to be higher, but I am learning that "spinning" is the key to going faster, not necessarily pushing harder on the pedals.
If you feel like you lack strength in your legs, get to a gym and work on the lower body but also do core strengthening exercises. A strong core is paramount to fast cycling!