Yes, which still put it below casters like clerics and druids. But that was the best that psionics had to offer in 3.X so I would say that it did a better job then of power parity.
I'd never complain about a class being 'only' Tier 2.
The 3.x Sorcerer, for instance, Tier 2, but a better class design with more potential for engaging play and covering more potential character concepts than the Wizard, IMHO.
Regardless of its terminological origins, psionics basically has entered general parlance for a type or flavor of "magic" within both science-fantasy - because the moment you introduce psionics into a world, it essentially becomes fantasy (hello, Star Wars) - and more traditional fantasy as well.
I can't agree. The point of psionics is that it is magic scrubbed of fantasy, religious, mystical or superstitious trappings, and draped with scientific ones, instead. Allow that "psionics is magic," and there is no difference between psionics and magic, at all, it's superfluous. You're down to psionics using different components or something to differentiate it as a different flavor of magic; or using novel mechanics to force a metagame difference where no meaningful conceptual difference exists.
That - and just plain the range of preferences among actual psionics fans - is why they really need to leave the magic-or-not decision to the individual DM.
However, psionics are generally not depicted as "spells," but as a subtle and mystical art.
Depictions of magic often include both what D&D would call rituals (lots of time, elaborate outlays) and what it might call 'psionic' (sheer force of will) or deride as superpowers (with no gestured/incantations/materials to speak of, and clearly an act of will and an exhausting effort) - rarely ever anything that might map accurately to a D&D spell (especially a 1e spell).
The psion probably has more in common with a 5E sorcerer than a 5E wizard. No spellbook. Smaller range of powers known. The main overlap between the psion and wizard has been Intelligence. That said, I know that the psion is most commonly attached to Intelligence as its primary attribute, but I know a number of psionic fans who would wish that the psion was appropriately attached to Wisdom for a change.
IIRC, the original D&D psionics was based on all three of your mental stats, wasn't it?
Though it'd be horribly MAD, and result in psions being dumped-all-3:STR/DEX/CON basket cases (like the other PCs might carry them around in a basket, because that slows the party down /less/) who look like grey aliens, the idea of having, say Attack Modes use CHA, Defense Modes use WIS, and Disciplines/Sciences use INT has a certain appeal.
In the 3e, the Sorcerer was early on the only option for nonvancian casting. Even then, at high tiers, the sorcerer was significantly underpowered compared to the Wizard
You mean, noticeably less overpowered. ;P