The major problem with Season 8, was that Riot changed so much at one time without any testing. The patch for Preseason 8 introduced over hundreds of different patches to the game. New runes, stat changes on EVERY champion, item changes, etc. There were tons of stuff introduced, now look at Season 9. You're looking at over 72 different patches this season to start off. Riot needs to stop doing these big patches, stop introducing new things like champions and reworks, and just flat out balance the game one step at a time. They need to add the stuff they changed in the first place that were already balanced as is. Minion gold changes need to be reverted back to normal for instance.
Mark my words, season 9 will be worse if Riot continues to do these big patches without facing the actual problem.