Goldfish is certainly under utilised, but I wouldn't call it underpowered. It's still a nimble ship (might not have any stat best but if utilsed correctly it can still survive much more than any pyra would. - Also don't rely on the numbers in the book too much, they arent entirely accurate (we know listed speed of either prya or Goldfish is wrong for example).
Goldfish's primary role is to force enemy teams into unfavorable situations, and it's still very good at it.
The only ship i'd say is screwed atm is the Poor squid (prya can still turn fast enough to keep it in it's arcs with help of phoenix claw -assuming squid doesen't sneak from behing the enemy ship).
Saying some weapons aren't for competitive play is silly (with exception of harpoon becouse that one isn't woring as intanded). Every weapon can work in competitive play - just all of the weapons are not equaly universal. We have won competitive matches by using gat-mine front on pyra. And that is certainly not meta.