Because it was the most competitive era thus far. Every team had strong IGLs and superstars at their peak.
NaVi with GuardiaN at his peak
Fnatic with the best IGL of the time and 4 god tier players.
EnvyUs with Kio, KennyS on god mode, Happy, NBK and Apex
TSM with Dev2ce, Karrigan, Xyp, Dupreeh cajunb. How are you supposed to get god tier stats against these teams?