I think at one point what you said was right, but due to the release of more and more ships (and an element of powercreep over time) some very serviceable ships have been pushed down the power rankings.

There are some pretty solid ships in T3/T4 like Phoenix, Ise, Leander Kai. Depends what tier list you look at. Shigure Kai, Gloucester, Rodney/Nelson. Not fantastic ships, but with the right gear capable of solid work in most of the not-end-game.

I think it is somewhat an arifact of the tier lists keeping the number of slots in each tier roughly the same, so even though ships are pretty decent, but they get pushed down by better ships as newer better ones come out. And with powercreep but also the devs understanding more what makes a ship good, each event brings more good ships which just continuously pushes more nad more ships down.