Riven?

That's a good thing. Although there are a lot of chmpions way more bullshit than her around nowadays

Getting dicked by garen in top lane

Champions tend to not get used when they are mediocre, and then receive multiple nerfs.

She was directly nerfed a few times.

Her core items were nerfed (Ionian Boots have less CDR, Brutalizer was removed).

Juggernauts became stronger (and they generally counter her).

etc.

V6.1:

Runic Blade.png Runic Blade
    AD ratio increased to 25%-50% AD from 20%-50% AD. 

V5.24:

Stats
    Health regeneration increased 5.34 from 3.34. 

She got buffs recently.

all in challenjour

Shes just been hit repeatedly by indirect nerfs and direct nerfs that caught up to her now. Imho i feel she needs help just like jayce both of them are under preforming atm.

She is good only in the hands of people who main her. Also most Riven players now spam Fiora. Also all the ranged ADCs are not a good matchup for her top - she has no sustain and gets destroyed, if she tries to cs.

I quote Hashinshin:

Grab Riven, screw around with her kit for an hour, learn her timings, collect freelo.

Thing is, alot of people are too lazy to spend that one hour getting to learn the basics of her kit. When there are other toplane champions that are just as strong, and easier to play.

etc