You can give your druid the criminal background and do not use a rogue, you can train your cleric in perception and survival and your ranger could stay home, you can use a half-elf sorcerer and give him the charlatan background so you do not need a diplomat, your half-elf rogue arcane trickster could be a sage and fullfill all your knowledge needs, you can use a gith hexblade warlock and you do not need another melee fighter.
I do not say that´s a perfect, but That´s something you cannot do in previous editions. Just saying.
Not being perfect and not being able to do that in previous editions, I agree. But the rest of the exemples you provided are almost all based on skills. Yes 5E has made it so classes can learn almost every skills. But saying, for exemple, a warlock Hexblade will replace a pure fighter, wich can get 4 attacks/round, combat maneuvers, fighting styles etc...you just can't replicate/learn class-specific powers abilities as you can skills
Again, as you said, not perfect. I say far from perfect.
