1UPT was proven broken already in civ5, there is no much to debate about it.
Districts, plit science and tech trees sure are new features, too bad AI is even more awful than in civ5 that you can lose game only in very specific situations. Most of other issues people are complaining and comparing are simply different features, are not really problems or there are mods fixing that issue already.
Hint: civ4 has mods to play using 1UPT but as I said, it is awful.
And about mods, sorry to disapoint you but civ6 will never have as many mods as civ4. Not to even mention complitely remakes like rise and fall. Civ5 already proved that firaxis dont really care about making game open to be modded, dare to look civ5 mods that list is very short. There isnt even a proper better AI mod.
Civ6 is like civ5, when it cant generate anymore cash new civ7 is released. It is not open to mod and AI is embarassing bad. It is not a game you will return 10 years later, civ4 is because modders are still developing it.