I think i figured out the main reason people ALWAYS despise new lore.
Because it no longer is "This character is..." A lot of characters are getting relationships with others and large backgrounds. When previously it was a short little paragraph that allowed SO much self-influence and guessing on the rest of it.
But now that Riot figured out actual lore and a story. People are upset their personal headcannons arent right. These characters that they once thought they understood every part of, based on a single paragraph and 10 to 15 lines of dialogue, they go completely elsewhere.
And thats not to say that they SHOULD keep old things in tact. If Vlad got a VGU and he wasnt a pun-master there would be problems. BUT characters need to be more than they once were.
The outrage around certain characters becoming Vastayan was way too much.
Another thing is people jump to conclusions WAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAY to fast. For instance, with all of these single paragraphs updates people are rioting that they arent what they want and they "completely changed the character" But riot understands that the old characters FOR SURE still need to be there. Remember when people first saw Viktor in Jayce's lore and everyone was up in arms that he was no longer a morally grey character? And pretty much the lore team said: "Just wait" and when his lore came out everyone was just perfectly fine with it?
People have way to little faith in the lore team. When FULL stories and lore come out i almost NEVER see a complaint. So why does everyone get up in arms at the littlest bit of information?