1. Apparently moon sugar is commonplace now, or perhaps literally the sugar of Tamriel. What happened to it being a rare, illegal drug?
2. There will be a fourth member of the Tribunal. It has been mentioned many times in-game that only 3 mortals became the gods of the Tribunal. This is probably the most powerful retcon here, if true.
3. Cyrodiil is no longer a jungle. In TESIV: Oblivion, Cyrodiil is not a jungle due to Talos having changed the landscape long ago (so it is said), but due to the time which Elder Scrolls Online takes place this would probably be before that.
4. Mannimarco is working for Molag Bal. Mannimarco is not a Daedric worshiper, he is a necromancer.
5. The Elder Scrolls are able to be captured for "passive buffs". This really belittles the Elder Scrolls. They are extremely rare, and hold vital information about the future and past (DO NOT grant powers!), but in most cases blinds mortals who merely attempt to read them. Are we all Ancestor Moths now?
6. Dagoth Ur is a mid-level dungeon boss. Again, more belittling. Dagoth Ur is immortal and it would make no sense for a group of people who are not the Nerevarine to attempt taking him on, as that would contradict the prophecy of the Nerevarine. Dagoth Ur deserves much more than being a mid-level boss if they're really going to have him be an enemy.
7. Argonians, Dunmer, and Nords are allied. At this period in time, Nords and Dunmer are more racist than they are in TES 3 and 5, and they would most likely fight for themselves rather than alongside alien races. Again, just another contradiction. Why not just, instead of having them be allied, make them the 3 independent races of ESO? If I recall correctly, Argonians didn't leave or care for the outside of their homeland at this time period (this is why they are a misunderstood race in the lore), which makes the alliance even more pointless.
8. The Tribunal needs an army to stop a cult in Cyrodiil from worshiping Molag Bal. The Tribunal are gods, and according to my info from earlier, they have an extra member now. Why doesn't one or two of them go down there and stop it themselves? This is just more belittlement of characters that are suppose to be very powerful.
9. Orcs are a playable race. First of all, I don't understand why this game is accurate with the lore only sometimes, such as Imperials not being a playable race in this time period. But other times it is not accurate. You know what else didn't exist in this time period? Civilized Orcs. They were seen as enemies, as they were mostly savage bandits and raiders. Nobody would ally with them period, and there wasn't an Orc faction to be allied with in the first place, Orsinium is destroyed during this time.
There are probably more retcons I'm missing, and I would appreciate anyone telling me those I missed. Anyways, even if half of these are false, that's still a bad way to treat a game which most people appreciate for its lore. I'm sure a lot of people would be deterred from buying the game because of this.