Because since then AA ranges of ADCs were mostly nerfed. Not every ADC got nerfed, but some of them, like Kalista
And Kalista sucks hard since they nerfed her range because it's massive the difference of aa range.
Back then low range was a meaningful handicap. Currently the best ADCs have same or shorter range than Vayne:
But those adcs have been meta numerous times in the past aswell (not Kai'Sa because she didn't existed ofc) while having "short range", its not something brand new to have adcs like Lucian and Ezreal as the best adcs and remember old Graves that would jump into your face to burst you on S4.
Looking at them you have Jhin and Draven that work on a similar way in the sense that they go for a few aa's compared to most adcs to deal their dmg, they are not forced to be all the time in range to perform, and worth to mention that both buy RFC as second (Jhin) or third (Draven usually). Both have way more actual range in the way they play than Vayne for their kits.
Ezreal has 550 range atack but his Q which is his main dmg has 1150 range and so his W for not even talk about his ultimate.
The only two adcs that are meta that are short range adcs are Kai'Sa and Lucian, Ezreal, Jhin and Draven are defienetely not short range adcs by the way they play.
You are only looking at the atack range but it's worthless to only see that because you could end up with the conclusion that both Ezreal and Vayne have the same range when it's not.