Considering I logged the entire experience of playing this thing, I know it's terrible, but if you had to point a gun to my head and said which was worse; POS or 76... I'm going to say 76.
POS, as horrid and lazy it was (it was a freaking Baldur's Gate copy-paste job, something I didn't know about during my playthrough!) has an endgame, was designed for a purpose (to try to make money to support Van Buren... by taking money away from Van Buren???, I dunno; ask Interplay about that one!), and was made from an era in which games were designed to be completed upon release (which isn't a compliment, but let's be realistic). The philosophy of video game design in 2003-2004 versus 2018 is like comparing the design of an outhouse versus a fully functional sewage system meant to tackle environmental changes for the next 65 years. In 2004, games were designed primarily to be fully functioning games that had everything in them, and their life expectancy would be limited based upon the culture surrounding said game, for the most part. Games today, if they aren't made by cheap shovelware companies (which still exist to this day that, ironically, adhere to the 2003-04 model of gaming still of just getting stuff out as quickly as possible), are designed with a goal of lasting as long as possible, with a life expectancy of a few years, given server usage, DLC, "events", and so forth. Fallout 76 was designed with the goal of lasting as long as possible with DLC and events to entice and further entrench people into playing the game.
And, honestly, another reason why POS hasn't been ported is due to the source code legality and also the music licensing; Bethesda isn't going to be paying a bunch of heavy metal bands royalties for a Fallout game when they firmly established that all music in Fallout is 1940s and 50s swing and big band music.