And I consider there being only "one spellcaster in the game that doesn't work like all the others" to be a damning indictment of a class-based game. The single biggest benefit of a class based system is that you can tailor it so different people can get what they want at the same time because that's what the class does. And if you're not doing that a class based system becomes an arbitrary set of RP restrictions and a sub-optimal form of point buy.
I'm of the strongly held belief that the Warlock, Bard, Artificer, and probably Sorcerer should all have their own casting systems. And that OneD&D playing it so safe is to its detriment.
And I think that D&D spell/magic system is a Strength of the system, rooted in history, proven to be successful, and there shouldn't be alternative magic systems at all in the Core game, just tweaks.
Let 3rd Parties create alternate systems. If they are popular, then good for them, they cracked the code and deserve the money coming their way. If there is an amazing Psion (or a Spellpoint caster) made by a 3rd party, play it. If it is so easy, fans can advocate for those great classes so others can play with them, right? If it already exists, Wizards can't copy it wholesale, so why compete. Or is it not easy? So many people have completely different views on what a Psion should be, and if people aren't going to agree, why demand that Wizards try to make something that will never get 70% approval?
All that said, I think Wizards will try again with Psionics in the future. It's a proud nail of a puzzle, that some designers would love to "get right." But it's not core, and it needs to have the right property to be released with, for context. If not Dark Sun, and if not Eberron (psionics are still not main-screen Eberron), then what? Maybe an alternate campaign/rulebook that leans into Psionics as the main "magic" like a pseudo sci-fi or a weird-fantasy campaign, or a dark modern investigative horror like Dark*Matter from Alternity. At least that gives reason for it to be developed to not mirror D&D Magic, so it can be its own comprehensive thing.