Not neglecting anything mate. Mercy has always been the to-go choice for a support for now 11 seasons. The only time and place she wasn’t was in dive meta which was only executed properly at the highest competitive tiers for a very small percent of the player base. You can close your eyes and ears but unfortunately statistics and numbers don’t lie and provide a clear picture, not touchy feelings or abstract things that are not measurable like “fun”. Fun is subjective. Mercy has always been the best solo single target healer with the most amount of utility/consistence and the least amount of skill required. That’s an objective fact and you know it.
“Can’t defend my own points so uhm go read this other dude.” 
The small #Revert Mercy cult and echo chamber is not a representative of the OW community, not by a long shot. Not even close. You can attempt character assassination and personal attacks but numbers don’t lie.
Yes, when one character is clearly better than everyone else, it is her problem. It’s easier to tune down one character than it is to bring up everyone else. More variables change and more things can break. This is a logical thought process.