Build/Position Diversity is not a good thing. Stop preaching like it is.
One champion is not supposed to be able to adequately fill in 3 or even 4 different positions. There are supposed to be downsides to lacking knowledge of positions, or intentionally playing as if you lack that knowledge. The same goes for items. You should not be able to perform well if you're building as if you don't know which stat your champion scales.
Simply put, there need to be consequences for playing the game poorly. You shouldn't be able to rely on a champion or certain build in a way that lets it completely overcome the downsides of picking the wrong champion for the position or picking the wrong items for the champion.
In essence, it's the same as the concept that you shouldn't have enough damage to 100-0 someone with a single ability even after you missed all 3 of the others. A champion or build shouldn't be powerful enough to overcome what would otherwise be hefty mistakes.
Ezreal, more than any other champion, often falls into not one but both of these problems because his kit allows him to abuse changes to items or runes intended for classes other than marksmen. Ezreal jungle, Runeglaive mid, and most recently the double-tear build. And the double tear changes coming in 9.6 are why I'm bringing this up.
Because they're perfectly healthy for bringing Ezreal in line. And people are actually mistaken in calling it build diversity. Any build that becomes the optimum for a champion is the exact opposite of diversity. It allows him to have total damage on par with the old AP Ezreal without the downsides, but also keep all the pluses of building AD since it still includes Gauntlet and his Q still scales AP as well.
That lack of consequence for building a mix of items that shouldn't work together on a single champion is why it needs to be removed. And I think it's the right choice to make tears unique-- because it doesn't affect any other champions. But it also doesn't unfairly punish a full AD or full AP build on Ezreal, which the only other option-- namely reducing his scaling of one or the other or both-- would do.
With those things in mind, what should actually be considered build diversity are things like the option to go either full on-hit or full crit, or full AP OR full AD. With the downsides that come with choosing one or the other. Where we have problems with such build diversity is when a champion's damage is just so high that they work well late game almost regardless of build, but that's usually easier to put in check by adjusting early scaling and/or synergy with income runes.
Edit: In summary, Exploiting game changes in a way that wasn't intended by their design is not a good thing. When Riot brings things in line to make sure champions have the weaknesses and strengths they're supposed to, they aren't damaging the game. They're only hurting the feelings of people who are abusing changes instead of using them as intended.
What they're doing with tear is no different from when they changed Runeglaive because it had the unintended effect of taking away AP Ezreal's main weakness.
Meh. At the end of the day downvotes from people who are wrong aren't going to change the fact that they're changing it. So kudos to you for voicing bias for a particular champion in the face of them receiving balance changes.
build in existence.