Matt your not being unreasonable..........maybe just a little unrealistic.
It's not just an Isuzu problem all of the utes have the same issues...........even way back in the 80's the Hilux Rodeo etc all had soft crappy suspension.
Aftermarket suspension is always better IMO and I factor this in when i'm looking at vehicles at purchase time........First major improvement on the LC 200 was to fit new suspension capable of doing the job day in day out no if's or but's.
I think of all 4x4's as a blank canvas from new and consider these upgrades as part of the never ending mindless money drain of what I think are improvements.
Yep 45k on a new car is not loose change and yes it should have suspension that is fit for purpose......but they don't unfortunately.
So if you want it right open your wallet once again buy the right gear first time around with new aftermarket suspension and enjoy it once fitted.....
IMO I suggest you look into Dobinson springs and Bilstein shocks...............stay away from the big chain 4x4 places and their systems......talk to a suspension only specialist.
Dan