I don't know if it's really possible to measure this. If anyone has any resources or data they can provide, please let me know.
However, I would like to point out that in the past the types of videos on YouTube have reflected the what people want out of Minecraft. Since the majority of new videos are of minigames or some sort of modified version of Minecraft, it'd be reasonable to assume that many people are no longer satisfied with watching vanilla Minecraft, and thus no longer completely satisfied with playing it.
Here is the video I was referencing that showcased a mod:
Now, Mojang doesn't have to balance two games. Is the game completely balanced when the keepInventory gamerule is enabled? Arguable no.
It's also worth noting that I am not saying we need to revert the combat system, because Mojang definitely shouldn't. However, I see no harm in creating a gamerule to allow people to have more control over the combat; many people prefer the simpler combat system.
Again, Mojang wouldn't need to balance two games. They don't have to balance the game according to any of the gamerules that currently exist.
There is no Poppy to Rose gamerule, no Food heals Health gamerule, etc. If you want to improve combat, a better solution is to suggest changes to the current system.
The rose being change to the poppy is a very minuscule change compared the combat, so this analogy doesn't make much sense. Plus, it can be very easily changed with a simple google and resource pack download. Food healing health, however, could be a useful gamerule.
Move forward, not backward.
Allowing players to adjust the combat to how they'd like it would be moving forward because it would be allowing people to play in new ways.