If you check out that link, you can see a balanced, well thought out video on someone explaining some common problems with Riven.
Watch the whole video if you want the key information and full detail.
He provides good ideas for nerfs such as lower E shield AD ratio or lower her HP regen at lower levels again.
He says champions like Urgot and Kennen etc who are good against Riven, have recently had nerfs or are going to be nerfed.
Also her builds provide her such tankiness and damage at the same time, even bad matchups aren't that bad for Rivens.
Another solid point is that Riven across many regions and ranks has positive win rate. In Platinum she was highest win rate.
People who aren't Riven one tricks are winning without knowing how to play the champ.
Also she is still the most one tricked champ and that needs to change.
I wouldn't change conqueror or spear of shojin because that would kill other champs. I would say lower her damage or increase cooldowns, lower health or armor or like that person said lower E shield AD ratio. Make it a lot lower. Someone shouldn't be rewarded a huge damage scaling shield based on a full damage build with DD that makes her tanky too.
She should be punished for building full damage/85% damage. She just isn't squishy enough.
Or a big change is to change her kit. Her kit currently is perfect for noobs. She has a knock up, stun, shield/dash and an AOE ULT. I don't disagree that it does require good combos however currently you can literally button mash most matchups without knowing your combo and win easily. She needs more risk to her kit. I want her high skillcap to remain high skill. Currently she is just too good at every rank and the runes and builds she has are too good that mean she doesn't need any skill atm.