I disagree. The two clerics you describe are still closer to the archetypal cleric than they are any other class, and the two fighters you describe are still closer to the archetypal fighter than to any other class.
So the dude with the rapier and the bow and the light armor is more of a Fighter than a Rogue? The robed priest of magic and stars is more of a Cleric than a Wizard?
I don't really understand your strong distinction, here.
The cleric is predominantly defined by its divine spell list;
...which included plenty of archetypal wizard spells as far back as 2e. The dude hurling fireballs and magic missiles might be a cleric, too (or even a fighter with the right magic items).
the fighter by its superior capacity for combat.
So the dexterous, sneak-attack-style stabby rogue isn't a superior combatant? Or the invisible, fireball-blasting, flying wizard or cleric?
Those two core concepts have substantial impact on the play of their respective classes. How would you conceptualize warlock play, given the descriptions of the three pacts we currently know about?
Don't mistake one particular thing about the class that it may have as monolithic and definitional. Any class can be superior at combat (CoDzilla!) or use a certain list of effects (priest of fire and fire wizard and fire psionicist and warrior in fire gear kind of hit the same notes). The more this is true about 5e, the more versatile and flexible and modular the game will be (ie: having a fighter in your party when you go into combat might not provide you any significant advantage over properly specced druid). In a game where classes are subject to redefinition and customization, it's the best way to go, so that you can release as many new classes as you want without invalidating the old ones.
So how does a warlock play? Well, with a blade pact she might play like a combat machine. With a book pact, maybe more problem-solving and effects-based. With a chain pact, maybe they'll be good at manipulating and dominating interaction scenes. Or maybe something totally different. No class is monolithic, no class has a niche that another class cannot acquire, no class is vital for any particular game task. Maybe your fighter is the best at combat, maybe your warlock is, maybe your rogue is. Classes in D&D are not just one thing. They are not even one kind of play experience. Given the varied play experiences many of the classes have carried in various iterations throughout the editions, WotC would be kind of crazy to tell everyone to play a class in a given way.
They'll have an "auto-pilot" mode. The fighter on auto-pilot will probably be a very good combatant. The cleric on auto-pilot probably will have a very particular spell list. The warlock on auto-pilot is likely to be a bit of a bard with extra Wizard cherries on top. But this isn't really definitional. Fighters can make mediocre combatants (2e halfling fighters!). Clerics can make crappy healers (OD&D "anti-clerics" with their inflict wounds spells!). Wizards can be melee machines (4e's bladesinger!). The basic version delivers on the basic story, but it's not the whole story of what a class is for the entire game (though it may be at your table). Warlocks don't need to be any one thing, they can be diverse and complex just as wizards and fighters and clerics and rogues can be.