Some crazy Star Wars thoughts while we wait for this whole thing to come crashing down.
Star Destroyers are the answer to ever-enbiggening military requirements during the Clone Wars, eventually simply containing all needs for a military venture under one command. As they have the entirity of an arsenal needed to take over a solar system, they become a one-stop solution to all military problems. Have some rebels? Send in an ISD. Some rebels get away from an ISD? Send a few ISDs. Vader lose his keys? Send an ISD. Need to subdue a population? ISD.
etc. An ISD is not mission-specific, but rather mission neutral.
Consider instead four smaller ships, each half the length of an ISD and each specializing. Dreadnought, carrier, Division transport, and supply ship. Each has a fraction of the capabilities of a star destroyer, except in one area where they meet an ISD. In all other areas, each of these four is lesser than an ISD.
For example:
ISD: 60 turbolasers / 72 starfighters / 9,000 troops / 40,000 cargo tons.
Dreadnought: 60 turbolasers / 12 starfighters / 250 troops / 2,000 cargo tons
Carrier: 10 turbolasers / 72 starfighters / 250 troops / 2,000 cargo tons
Transport: 10 turbolasers / 12 starfighters / 9,000 troops / 2,000 cargo tons
Cargo: 10 turbolasers / 12 starfighters / 250 troops / 9,000 troops
Now, imagine a a fifth vessel. While an ISD has the firepower to go versus a
solar system, this may only be able to subdue a planet:
Victory Star Destroyer: 20 turbolasers / 24 starfighters / 1,500 troops / 8,000 cargo tons.
That is: At this level, there are specialist vessels and still room for a vessel that has a wide variety of missions it can take on. It would not be able to take on as wide or as deep a mission parameter as it's larger sibling. While an ISD has many ATATs, different weather gear for troops, specialist starfighters, and the firepower to decimate a small fleet, the Victory star destroyer is missing the specialist cases.
Finally: There could well be generalist-ships like a Star Destroyer at the 800, 400, 200, and even 100 meter ranges. Admittedly, at the 100 meter, the ship has one starfighter and barely deserves to be thought of the same.
Ships needed a crew of around 10 are in the 50 meter range. This includes Free Traders, Firefly, Pirate ships, etc. At best, you get two externally mounted shuttles as subsidiary craft, not dozes of star fighters.
.... You guys, for whatever reason my brain will not stop doing this math. Over and over again. It's like a fucking loop.