Per
@mellored OP's mission statement; as of this post the classes with the least identity are sorcerer (51), fighter (45), wizard (29), and ranger (26). After this, there are a cluster of classes in the mid-teens: artificer (14), warlock and cleric (13), barbarian (12), bard (11), and rogue and monk (10). Lastly, still in single digits, is paladin (4) and druid (2).
If the goal stated was " if D&D had to reduce the number of classes, and they were going to remove the ones that has the least identity, which ones would go?" Then an interesting conundrum develops: you remove the two martial classes with the weakest mechanical identity and the two arcane classes whose identity is "casts magic". That is; the "I hit stuff" and the "I cast stuff" classes that don't speak to any single archetype are the most bemoaned. What do we do about that?
Arguably, you could just smash ranger into fighter and make sorcerer and wizard one class again and be done with it, but I don't know if having them absorb another class would help the whole "no identity" problem. Alternatively, you could break the sorc/wiz into thematic casters (warmage, beguiler, necromancer, summoner) rather than a division by origin/casting mechanic. The fighter could probably stand to break into a couple different martial classes (warlord, cavalier, skirmisher, gish) of which the ranger could be mixed into. But what I find most interesting is that this really breaks the notion of the "generic classes, custom subclasses" since per the OP, the generic classes were the ones highest on the chopping block.
Or, alternatively, most of the voters didn't read and the whole thing a popularity contest and petty grievance airing. And so it goes...