A ship's class type is not some set in stone checklist of criteria. It's all about roles.
And while yes, titans and battleships are generally bigger than destroyers, this is due to their role, and as ships need more capability they invariably get larger.
That aside, a ships class is totally dependent on the person whobfesigned it. What if some of my ship classes don't fit into any particular box?
IRL, no navy knew exactly what another navies ships really were, unless that country stated it. All they could do is look at the guns, and dimensions, and kind of male am educated guess. Nazi Germany's cruiser Admiral Graf Spee was referred to as a "pocket battleship" because to the English it certainly seemed more like a battleship than a cruiser. But it certainly was a cruiser, and was used as such.
Anyway, my point is this: DONT TRY TO FIT ME IN A BOX MAN! Lol
I have nothing against anyone's particular "class" system but leave me out of it. Any sort of organizational list like this should be limited to whomever you play with. Merely having it as an option is totally superfluous.
Of course, I am always open to being swayed. But when I was younger I was obsessed with catagorizing every vessel I ever saw, both real and fictional, and I finally discovered that any sort of actual system is loosely defined at best, and works simply because everyone ahrees on it.