"Spell" is just a container. You can put whatever you want into it. It's main use is to balance and limit effects.
So I don't see how renaming Fireball into a "Power" would change anything except maybe sounding a bit more universal.
But please explain what you see as the difference.
Calling it a "container" means it has no effect on the shape of what you put in it. That's flatly not true.
Spells--specifically focused on "full" spellcasters here--have a specific structure for:
- How they are gained as a resource (a specific fixed schedule of slots)
- How they are learned (roughly, 1-2 per level)
- How their potency is distributed (ten levels of slots from 0=cantrips to massively powerful 9th level spells)
- How their potency is designed (e.g. 3rd level spells generally do XdY damage)
- Spell components, and both the thematic and mechanical costs/limitations these entail
- How they interact with other effects (AMF, counterspell, etc.)
- What kinds of AoE they can have
- How their effects are centered/located/etc.
- It forces everyone to abide by the same restrictions on when an effect becomes accessible
- And many more
"Spells" is not JUST a container. It's a container of a very specific size and shape that can only accept things chopped into the correct shape. That's why you (and WotC) felt compelled to create exemptions to the component and interaction rules--because those are one of the numerous facets of what it means to be "a spell" and their removal does do something (albeit not very much IMO) to move away from what it means to be "a spell".
Or, to turn the above into a "what limitations does 'spell' induce?" direction:
- You can't design a class that gains more new...let's call them "knacks" early on, but fewer later, e.g. tier I at 1, tier II at 2, tier III at 3, tier IV at 5, tier V at 7, tier VI at 9, etc. (so 1/1/1/2/2/2/3/3/3 which works out to 18 levels overall--comparable to but quite distinct from spellcasting)
- You can't design a class that only learns "knacks" infrequently, but in larger chunks (say, 3 at a time), or where knowing one low-level "knack" guarantees you will then pick up a higher-level "knack" later on
- You can't design a different distribution of power, e.g. only six tiers of "knacks", or 12 tiers, or 20, or what-have-you
- You can't make different choices about what counts as balanced vs imbalanced in terms of damage output or effect
- You can't just willy-nilly ignore components (hence why WotC's exception still requires M components consumed, or with a cost)
- You can't just willy-nilly ignore interaction with other effects
- New types or variations on areas aren't permitted (e.g. an effect which makes multiple parallel lines isn't compatible with 5e spell AoEs)
- New modes or aspects of targeting aren't permitted
- Effects "out of sequence" from spells can't be added--so, for instance, no spellcasting Psion can form a group mind connection until they reach level 9 and get access to Rary's telepathic bond
Spells lock us into a large number of design assumptions and limitations. Supernatural power
in general does not limit us so--as we can see in the sadly limited tracery of non-spell supernatural powers available. By not restricting ourselves to the design space of "it has to be spells and only spells", we gain a huge design space to play with that, if we remain serious about keeping psionics distinct, really does offer a number of ways to do things differently.
And all of that is without even touching that "if it looks like
fireball, if it sounds like
fireball (etc., etc.) then just let it use
fireball" isn't a valid argument, for several reasons. It presumes that all spells are as basic and as simple as
fireball, that
fireball is the only meaningful way an AoE fire damage ability could manifest supernaturally
and mechanically, and that most if not all Psion abilities would simply be 1:1 equivalent with an already existing spell to the point that any effort spent designing it would be indistinguishable from just doing the same spell with incidental tweaks (e.g. an Int save instead of a Con save or whatever--that's small enough to be incidental.) Most spells are rather more complex than
fireball, there are many different ways AoE fire damage could occur both in terms of thematics and in terms of mechanics, and there's no reason that Psion abilities would track anywhere near that closely with spells,
especially if we do as implied above and aim for different resource schedules, different rates of acquisition, etc.
Which, I agree with
@Scribe that it is very much not a trivial task to do this. Unfortunately, I also agree that WotC is too lazy to actually do that amount of design work, and will
almost guaranteed end up sticking with a pure spellcaster that is
functionally "Wizard with actual class features and fewer spells per day". But you miss 100% of the shots you don't attempt. I can hope that there are enough "psionics is NOT spellcasting" folks out there that could convince WotC to change their minds. It worked with the Warlock, after all. It could work again.