Disproportionate Pressure Bottom Lane
I believe the strategy of "Let's all just asspound botlane and take tower so our best objective taker can roam and fuck the rest of the map" is so consistently strong that it is rarely correct to deviate from it.
This really detracts from the strategic depth of the game in my opinion. Of course it's a multifaceted issue, it didn't help they included changes that facilitate snowballing, but there just isn't enough value top lane*.
*Unless you have an aids champion like
who can take rift herald and proceed to never leave lane again.