They were supposed to do too many things.
And, nobody listened when the smart people said so. When toldto select 2 of 3 out of quick, quality, cheap, they said "Yes, all of those!"
They wanted a super-fast ship that could be sent to troublespots rapidly. They wanted a smaller crew to man the thing (lower costs). They wanted it to only carry "necessary" equipment (also to reduce costs). And, they wanted them built quickly at a low unit cost.
So, the theory was to have "modular" weapons fits (and crewsspecific to those)that could be "plugged in" to need. Because that takes time, they needed to be fast, very fast.
Fast meant light, too. So, the would up with AL hulls. They also needed fast, so they wound up with COSAG propulsion to drive the jet pumps needed for speed.
So, the reduction gear boxes wound up being a major issue metalurgically. Especially with the sort of hull loading a 40kt vessel experiences. They wound up with issues about mixing the AL alloys used (there were predictions about welding such things). They wound up with galvanic corrosion issues (also precdicted). That's what "sank" the first 12 produced.
Turns out "modular" is a dumb way to fit out a ship. Especially if you expect to sail it a few weeks out of Home Port (this was predicted). So that was ditched. Turns out the compromises needed for CODAG (especially a marine Diesel with two different RPM ranges) were a mess (as predicted). They had issues with either the gas turbines (chosen for weight, not reliability) as well as the Diesels (also predicted). The reduction gears also had many engineering casualties.
Then, the rather puny mix of the 57mm autocannon and a glorified Stinger missile fit was anemic. The Oto-Melara 57mm unmanned mount turned out to have a lot of problems in real life (around a 50% casualty rate).
Those last two are what are "sinking" the rest of the fleet.
What they wanted was a glorified CG Cutter, only without asking any Coasties what actually works.
Well, actually, they wanted a Des Monies class Heavy Crusier that could operate at 50-60kts, and cost less than a Frigate, and maybe carry 30-40 a/c and a battalion of Marines with landing craft, too. And nobody told them "No."
There are some wags pointing out that Kathy Giffords is going to out last the ship named after her.