I reckon that it's the significance of skill that's causing the majority of the hate towars 1.9. Almost anybody could pick up Minecraft for the first time and know exactly how to dominate in PvP, through accuracy and spam-clicking, and techniques such as 'cirlce-strafing' or 'w-tapping' which took mere minutes to master. PvP was an effortless activity that required no skill and had a very thin skill-gap. Now with the addition to 1.9, it requires timing, loadouts that cannot be relied on, accuracy and strategy, and the skill-gap will be much larger between players as it's no longer a matter of who's ping is better, or two can click the fastest. It'll take time for players to adapt to the new PvP algorithm, which is why players would rather stay in the past.