While "modern" is a pretty much relative term, (I have a 1952 issue of "Modern Railroading" sitting on my shelf...) the prototype for AM' "modern" tank car hails from the 1980's, the Railbox cars from the mid 1970's. Some of the S Scale America cars are somewhat newer prototypes, but are also getting long in the tooth.
None of the TOFC cars by either AM or MTH would be in service today. The AM spine cars and SSA well cars are also past their prime.
The AM and SSA cars are at best stand ins. They are less representative of contemporary railroading than they seem. There's no BNSF swoosh, (well, MTH has it on an outdated PS-2 hopper) only two NS and one CSX car in the AM line and no contemporary Canadian Pacific to be found. Most of the roads offered by AM are long gone.
Also, except for the outdated MTH NS and BNSF PS-2 hoppers, absolutely none have the conspicuity striping represented that is mandated by the FRA on all freight cars since 2005.
Rusty