There tends to be a perception that capability is solely a factor of bolted on systems when platform is a very big part of it.
The platform is what gets the mission systems (whatever they be) to where they need to be, supplying them with power, cooling, and a stable, survivable, platform to be used from.
An Armidale or Cape Class PB is a good example of this. Below sea state 4 it is perfectly adequate, above it is compromised to the point of being unsafe to operate. Add any form of resistance, even ramming by a fishing trawler, they are useless. But on paper they are vastly superior to the more survivable vessels (Fremantle and Attack Class PBs) they replaced.
The Arafuras are more seaworthy and durable than any of the PBs but they are still not warships.
Even among warships there are major differences in durability and survivability, not all relating to physical size.
I'm speaking of compartmentalisation, ballistic protection, fire zones, firefighting systems, reserve buoyancy, structural strength.
You could literally strap a Typhon container on the mission deck of an Armidale but it still wouldn't make it a warship. It's basically equivalent to pintle mounting a .50cal on a Hilux, it gains hitting power, but it's still not a survivable combat vehicle.