The Old Lore -- Glad It Is Hopefully Going Away
And the main reason is simply because it doesn't make any sense that figures like Aatrox, Vel'koz, Bard, Nocturne and many others would be fighting, or choose to, or even be trapped into the Fields of Justice. 0 sense.
Bard -- Gave up on world saving for...? Team-oriented games? Lol?
Now, any of the pure evil characters (embodiments of evil -- not talking about Noxeans, but spirits and whatnots) wouldn't ever choose to fight in the League, and I doubt someone like Aatrox could be trapped by magic in there. Ofc it's fantasy and fiction, so Aatrox could technically be forced to be there, if the writers write so... But it doesn't feel right -- very hardly it would make sense. Same goes for Tahm Kench -- if you understood what Tahm Kench is, you would see that there's nothing for him to feast on in the Fields.
I understand what happened over time with Riot when making new champions and respective lores, and also why they are changing it now, the longer they take to do it the worst. The more champions and lores are added, the less it all makes sense.
What about Yasuo finding the Elder's muderer? Oh no, nevermind, he's at the Fields of Justice. Basically, this explanation/lore doesn't fit what League is now.
Will Nocturne torment more people? Some bulls*t about summoners getting ill when summoning him.
What about Nocturne being Zed in the future? Noc can be his nightmare, but he cannot be Zed himself, as both are in the Fields. Again, reading it all, alot of it doesn't make sense.
So yeah, embrace the short bios and new stuff you're getting now. I believe something better is coming, and it may not be this Bilgewater event but in the future. Something to encompass everything. Some good explanation on what are we doing when we play League of Legends might take some time.
EDIT: Sorry for the bluntness and haven't read 99% of the old lore.
Indeed I did not read all journals or whatever it is named. I know the basic from friends, here and there, that we players are the summoners who call upon the champions to fight over a match to decide real Runeterra triffles.
And reading only a few lores, from champions I'm using as examples mainly (Noc, Aatrox, Yasuo, Zed, Bard, not much of a lore that one and a few others I'm not recalling now) and, the current summoners explanation sucks and doesn't FEEL SMOOTH. It's forced.
I understand your attachment though and Riot is kinda of slapping you all from those times where champs were made to fit the lore.