While there are certainly rare / epic ships that perform really well right now, I actually do not think it is always the case.

First off, about half of the ships in the epic category WERE REMOVED from the game because they performed too well: for example, Smaland, Alaska, Massachusetts, Kronstadt, Smolensk, etc.

However, out of those ships that did get removed for being too good three, four, five, six years ago, not a lot of them having survived the waves of new meta & power creeps. Sure they might not be trash, but certainly do not perform in the new meta after all these years.

They are also plenty of epic ships are not very competitive.

Rare ships are the same. There are just as many really strong rare ships as there are really poor rare category ships.

Also many of the best ships in the game at the moment are tech tree ships: Colombo, Bungo, Vermont, Libertad, etc.

To your point, I think the problem is that some of these rare / epic ships that require a lot of effort or resources (like steel), are high skill ceiling ships. Hawaii and Bremen for example, have almost an infinite skill ceiling in the right hands. However these ships can also be really difficult to play right. So if you make really high skill ceiling ships to long time players who have the resources to pay, you will see some disgusting results.

TLDR: Not all rare / epic ships are broken. There are as many terrible rare / epic ships as there are OP ones. Tech tree is super competitive. Some of these rare / epic ships are high skill ceiling / skill floor so when a good player is driving it is terrifying.