The problem with railguns is that chemical propellants are just really, really good. The main thing that came out of the railgun project (pictured in this meme) was the projectile that can survive extreme acceleration and maintain incredible accuracy. It is just better to shoot said projectile out of traditional gun instead of the railgun because the equipment required to run the railgun is huge and the projectile will fit in an existing terrestrial howitzer. That said, the equipment size and energy requirements really aren’t a huge problem for naval applications, but then again you can do the math and find that an equivalent size of traditional gun can sling way more mass per hour than the railgun can and you can make a hundred of them for the cost of one railgun.