Sorry what? All sorts of weapons from the war are being used, even many German such like the MP40 and MG42, and no self-respecting "first world country" would allow itself to arm unreliable Soviet piece of shites in weird calibers, even if they made millions of them.
I challenge the assertion that Soviet arms are “piece of shites” or that they are in weird calibers.
With some exceptions that have since been removed, Soviet block arms are just as standardized in caliber as western ones with you getting a singular pistol caliber (9mm Makatov vs 9x19 NATO), intermediate rifle (5.56 nato vs 5.45 Soviet or 7.62x39) full sized rifle/GPMG round (7.62x51 NATO vs 7.62x54R Soviet) heavy machinegun (.50 BMG/12.7x99 NATO vs 12.7x108 Soviet)
So with the exception of having both 5.45x39 and 7.62x39 for intermediate calibers, the Soviet system is no more complicated than the NATO system. Plus most places use only 5.45 or 7.62x39, not both, with the exception of bigger countries like Russia itself which can handle the supply issue.
As for reliability and quality, Soviet arms are damn good. The reason we see them as “cheap crap” is because AKs are already paid for by the former Soviet states and on the surplus market you’re getting s huge discount. Parts kit build AKs in the US that were mostly already high quality Soviet parts only need a few cheap add ons to make a complete rifle so it can be sold as a very affordable price. To make an AK to old world 1960’s standards would cost even more than making an equal quality AR-15/M16, which is exactly why current manufacture Arsenal AKs made in Russia cost upwards of $1000 compared to a comparable Colt AR-15 (model 6920 for example) is about in the $800 range.