Pre-season right now is very snowbally and some champs reap the benefits.
Rageblade: with the addition of guinsoo's rage on full stacks it is incredible cost efficient (roughly 40 md on hit, 54 AD, 72AP, 64% atk speed) and a hydra effect for fast pushing. Xin/Jax/Irelia types of champs are loving it!. Their ability to fast stack it and stick to targets makes full use of it and therefore spike hard in a snowbally meta.
The downfall of standard AP mages.
Their burst/range and disengage power allows for rageblade users and adcs to have the time of their life.
Champions such as Lux, Veigar etc.. Which used the now nerfed ap items fall behind and they could punish the all in bruisers and lower ranged ADCs. Not much now stops above mentioned from wreaking havoc.
The new AD items and the easily availanle crit. The ADC powerspikes harder in mid, but damage is lower late, due to how much worse the new LW is overall. However it rarely goes that late due to snowballing and ADCs become overbearing.
AD assasins, those that used crit items and those that relied on armor pen. Talon/Rengar rejoice! High burst with new items benefits a lot. Zed/Riven, rumoured to shine.... Nope, the brutalizer removal and LW bad against non tank, hit them hard. Base armor that they could shred/ignore got a lot harder to pass and they got nerfed hard. (Also they cant really deal with guinsoo champs that easily)
Supports: TK still broken, soraka: masteries made her orgasm and explode into more heals, now with resistances as a bonus!
Lane bullies shine, with fast meta they can snowball hard. Leona/naut/sona are strong laners and do well with their hard engage in mid.
Junglers: tanky junglers do really well with masteries and hunters potion, can sometimes lack in the translation phase due to not benefitting as hard from snowball/early aggression.
Guinsoo users: self explanatory, if not already explained.
Strong early game junglers: it is a fast meta... Does it need to be explained?
What do I think is overlooked? AP champs that does not always go into the now nerfed ap items.
Azir: not many can play him (I am working on him, he is quite fun), but he is good at zoning guinsoo's and can outrange ADCs. Does need a but of scaling... A bad azir is a minion, a good one is The emperor.
Malz/Annie/Brand etc.. Spike hard with different builds, generally those who builds flat mpen and spike hard with 1/2 items.
But!! The #1 reason IMO.
People. They deal bad with changes, are stubborn and only want the "old days". Does not try to work around changes and instead complains about X is OP AND!!
People for some reason gives up so easily, even though it is snowbally, you can still comeback. And you can come back fast! Return snowballing is real, but far too many give up, pre-season mood maybe?
P.s I forgot mastery discussion for ADC/assasins/guinsoo's, but some of course benefit more than others.
For those who complains about yasuo/trynda. Yes they are strong, but not overly so(with WB nerf), either ban or abuse them. Malph/Jax/rammus can easily counter them.
Tl:dr work around changes and stop giving up, life moves on and some really needs to acknowledge that.
It is early so I likely forgot a lot. I hope this helps and comments would be nice