I suspected that if WOTC didn't drop the backwards compatibility shtick that they were going to end up causing a huge problem, and we learned today they chose to double down on it.
The game already struggles with class disparities, and now they're definitively giving people the ability to assert they be able to use the, likely to be, overpowered versions of the classes that won't be seeing any changes.
So unless OneDND as a whole ends up upscaling the power of everything across the board so that nobody wants to use 2014 (not good either), then its going to be a mess for DMs to deal with.