Nah. Far far from the dumbest. If anything, it was a great idea that helped bring much-needed conceptual clarity to the classes. It's why they made great choices in 4E Darksun that outshone the original 2E setting. Power sources were great for tying the classes into the core concepts, themes, and magic of the D&D universe, and they should be brought back.
I completely disagree. I never played any previous editions, but I love the power sources. It just makes sense to differentiate the classes.
Your problem isn't with power sources. Your problem is how 4e used power sources. The 4e design team was too strict in making every base class use one power source and stick to one role. In D&D many classes are multi-source and multi-role in archetypical mechanics.
Debating Zardnaar about anything 4e-related is pointless, as Chaosmancer said. Zardnaar fervently dislikes nearly
everything 4e. As for my own two* coppers:
I hated mixed-source classes. Still do. "Power source" is descriptive
so it can be useful.
Some difference exists between Cleric and Wizard beyond names. That matters for both design (e.g. effects balanced for Divine chars generally, but not for ALL CHARS
EVAR) and for player aids (e.g. Primal-focused picks
should be better than generic ones for Primal classes). Casually discarding those benefits is foolish!
A main beef with sources was the insulting term "grid filling." E.g., accusing the designers of creating classes ONLY to "fill spots on the grid," lacking other reason or merit. But this
never happened. Consider the (aforementioned) Shaman, or the Avenger, personal favorites, which did new, interesting, and
flavorful things beyond "grid filling."
Shamans existed in 3.x, but 4e's version is pretty distinct. It followed Druid by being Primal; however, but was far more
spiritual, arguably the most spiritual 4e class. It even summoned a spirit-ally, but spirits saturate its fluff AND crunch. Many Shaman actions conjure temporary ally spirits, or employ the Shaman's spirit companion. The flavor of both the class and the world developed this further.
The other main Primal classes all take at least a somewhat
instrumental view of the Primal Spirits. All Primal classes revere them, sure. But Warden, Barbarian, and Druid were
using that power, not
for the spirits, but for something else. Wardens channeled spirits into their bodies, Barbarians entered altered states of consciousness. Both achieved a kind of transcendental
union with the spirits to
do things. Druids could clothe themselves with animal form, again for some other goal. But the Shaman asked
the spirits themselves to join in. Not to donate some of their power for personal use, merge with the Shaman, nor permit mind or body emulation thereof. Shamans treat spirits as equals, walking with one foot always in their world. That's huge for me, and something I've relied on since. That Druids are about the Eternal Now and the Living Cycle, and Shamans are about the Moments of Transition and Unending Journey. Two sides, one coin.
As for the Avenger? Just need one name to justify it:
Assassin's Creed. The "holy killer" is
not new, and fits well into pseudo-medievalism,
especially as we expand that to include the influence of Golden Age Islam on the Medieval Period. We've just been blind to it because "divine magic is for
healing and
support." AKA: designers were blind to a (narrative and historical!) archetype purely because a box
didn't exist for it! The Avenger also had the trial run for Advantage as its key damage benefit. And it did so while covering a very real, and very long-neglected, narrative hole in the relationship between the gods and their mortal agents: how the gods deal with
betrayal.
Mortal betrayal of godly trust is hardly new (we've had the Blackguard since, what, 2e?) But the only tool to address such behavior was a
problematic one: pulling the plug. In the wake of 3.x, most agreed plug pulling had...flaws. It tacitly encouraged unhealthy DM/player relationships, and made many interesting plots (like gods changing their minds or internecine warfare) nearly impossible. 4e's Investiture idea fixed these problems, but left a hole. (5e's silence on the subject is...well, I guess a "solution," in the sense that "I dunno, you figure it out" is a solution to anything...)
The Avenger fills the remaining gap, by articulating what the gods do when someone betrays their trust. They send in the hit squad, the divine Internal Affairs. That's such a cool idea! It says a great deal about the gods (that they must be very cautious with who they give their powers to, that they seek high loyalty in general and
especially high loyalty from their Avengers, that they consider the possibility of betrayal and plan accordingly, etc.), it creates new and interesting scenarios for both player-fuelled stories (hunting down heretics or BEING the hunted heretic!) and for DM-provided ones ("a traitor to the faith of Lolth wants your help fighting off Lolthian Avengers come to kill him!" or the like).
So yeah. TL;DR: "Grid filling" is not only false, but the only thing even
like it actually resulted in really cool new ideas. And mixed-source classes sacrifice a clear benefit from both design AND play-experience...typically for meta-aesthetic reasons that do not actually help make a better game.
*In this case, two coppers buys you a lot of words. I'm generous like that.
Watch the language, please.