Joining my voice to those who say that spellcasting mechanics have already been unified.
All spellcasters cast spells: prepackage magic of limited versatility. No class perform free-form magic.
All spells have a duration in time measured in rounds, minutes, or hours; not « until sundown », « or until someone sneezes », or until you learn to love another » etc, and no specific class modifies that.
All spells belong to one of the eight school of magic. No specific class escapes that.
All spells have either verbal, somatic, or material components. No class brings other components such as « the moon must be visible », « the tide must be at its lowest », or « must bathe in blood » mechanics.
All spells require a spell slot of equal level or higher. Some spells do have enhanced effects with higher spell slots but that is not class-exclusive or class-related.
Spellcasting stat differs between Cha, Int, and Wis, but the calculation for attack rolls and saves are the same for all classes.
All classes that use the same spell cast it at the same spell level. Fireball is always a 3rd level spell if you have access to it. No class casts fireball as a 2nd level spell for example.
Spell slot progression have been unified, only, some classes advanced at half speed in the progression (or third speed with arcane tricksters and eldritch knights), but the progression is the same. Warlock are the exception here; I’ll give you that.
In addition to warlock, there are some differences, discrepancies, and incoherences, such as…
Some class have the ability to cast ritual spells without spending a spell slot by increasing casting time, while others don’t. That’s one discrepancy. This could be unified to all spell casting classes. Similarly, some spellcasting classes (rangers and paladins) don’t have default access to cantrips, another category of spells that do not use spell slots. That’s indeed another discrepancy.
The artificer has a weird exception when it comes to multiclassing. That’s another class-specific discrepancy.
Classes are either spell known or spell prepared. Wizards must prepare spells within their spells known. Among the spell known classes, progression is not uniform. There’s potential for uniformisation here.
as for the rest, the fluff is different, the narrative is different, but the mechanics are the same really.