I am a huge Psionic fan. I love it because of its theme and its INNATE personal magic.
The magic of a Human mind is also the magic of any mind, even the "minds" features of nature, like mountains, rivers, storms, and so on. Psionic is the closest D&D has to animism. When we look at the Viking Norse, the American Indigenous, the Aborigines of Australia, and the Traditional Religions across regions of Africa, and so on, these translate best into D&D via Psionic. Minds interconnect including the minds of nature, such as Psionic mountains and Psionic rivers. The world is a community of neighbors with interpersonal relationships. Each person is a presence and an influence.
Each "soul" includes mind consciousness, ghostly spirit, and ki aura.
What I dont want from D&D is unsupportable unintegratable fringe mechanics. No more Psionic ghetto.
With regard to the Psion class it is a spellcaster. It is normal magic, but there are important mechanical requirements that are currently missing in 5e. Spell components must be deleted from the spell descriptions. Each class has its own method for casting spells. A Wizard requires material components including a wand. A Bard never requires them, and should only use Verbal, but a subclass might instead use a music instrument or Somatic dance. A Psion uses ones own mind. The spell description gets in the way. Each class does its own thing. Each class has its own method, including the Psion spell caster.
Psionic needs a few more new spells, such as better spells for low level telekinesis and low level teleportation, that are powerful and feel "psychic". But the spell system works well, and balances carefully to ensure the balance and stability of the 5e game engine.
When I look for a Psion class, I am looking for the D&D tradition of the 3e Psion, which is a full-on spellcaster. For a 5e version of it, the Warlock chassis with short rest spell points works best for mechanical feel and game balance. The chassis has powerful at-will abilities, energy-depleting spell capabilities, and high level novas. In place of Warlock Invocation are various adhoc Psion features that may or may not be spell-related and that a player can choose from.
The Psion class is fully a normal spellcaster. But other Psionic concepts dont refer to spells. It is ok that the Psi War and the "Soul" Knife lack spells. Their Psionic concepts are magic, but arent spells.