Generally, even in hard games, you can make one mistake and still live. In League I rarely ever see someone survive a full spell rotation. The last game I played, every single death people would just get deleted instantly and just go "WTF???" in all chat. That isn't fun, your kills feel like bullshit, your deaths feel like bullshit. Everything after laning phase is balloons covered in needles.
Let's say a 3/0/0 Zed attacks a 0/1/0/ ADC while he's alone, the fed Zed should still need some auto attacks to kill him, the ADC should be able to survive if he dodges Zed's combo or kites him really well. At the same time that Zed shouldn't get two shot by the ADC lategame for walking within 500 miles of him. You get locked out of the game for 50 seconds for a death that happened in 0.5 seconds. That isn't an exaggeration, that's a common occurrence and probably happened to everyone reading this who isn't a tank main in their last ten games. That's not fun, that's not even gameplay.
The way that scaling works also means that after laning phase the losing team will almost never be able to beat the winning team. The losing team's gameplay becomes 'Try to stall for 30 minutes until you have 6 items' the winning team's gameplay becomes 'Try to entice them into coming out of their turtle so you can delete them.' That isn't fun. It's pointless for the game to continue past laning phase. 1/15 games being able to comeback because someone on the enemy team AFK'd, got ridiculously overconfident or randomly decided to start tilting their team doesn't cut it. Surrendering doesn't cut it because nobody wants to lose either.
In URF if you get behind, you can actually still make a comeback because -both- teams do ridiculous damage so if you -outplay- the enemy then you can beat them and win even if they have better items. That's a proper League of Duty and it's fun to play, but regular League can't be that. What this game needs is for combat to take more time so there's more time for your skill to shine. It has to be more balanced so the enemy team is more threatening than the minions at all stages of the game, so that even if you're light years ahead there's always that "What if?" and so that even if you're light years behind your hope is legitimate and you can wrench it into reality if you can pull it off.