The fundamental problem with this specific assertion is that the warlord doesn't exist.
Again, this isn't 4e , this is 5e. Aside from a 1-to-1 translation of warlord being clunky and overbearing in 5e, the warlord's abilities have, indeed, been displaced about the various different classes and would suffer from lack of identity.
Bards inspire on the battlefield, heal from a distance, augment other character's attacks, and have some shared martial aspects.
Paladins incentivizes cooperative play through their auras, stand resilient when faced in melee, and are able to protect others from a distance
Sorcerers remain in the backline while controlling the battlefield but are more resilient than most other fullcasters. They can do great damage from a distance while also providing some of the best support abilities in the game.