That's a mistake they've made in every edition so far.
Basically, they figure out a broad spectrum of supernatural stuff that characters should have access to, and at what levels. Then they make most of that stuff available to wizards at those levels. So, for example, if they think outright mind control should be available at 9th level, they make dominate person a 5th level spell.
Later, they want to make more focused, flavorful casters. But since they've already given the wizard all the goodies, there's little design space left for what other classes should be able to do, so they have to focus on gimicky casting methods instead (like power points/pumping for psions in the XPH, or the methods for binders, shadowcasters, and truenamers from Tome of Magic). What they should have done instead is narrow the amount of stuff they let wizards do, thereby leaving room for other classes to fill the void. I think the closest they got to this ideal was actually 4e, where the PHB wizard focused heavily on elemental magic and force magic, with a little bit of illusion and almost no mental magic.
I think, as others have pointed out, that arcane magic should be broad in scope. People expect wizardly types to have access to all sorts of abilities at once, masters of utility and choices.
However, I think they should be less...focused in power, except for the big flashy stuff that wizards and the like are most known for. That is to say, giving arcane magic access to most of the TYPES of abilities in the game (honestly, probably even healing since in many stories of old, wizards and witches and the like can heal wounds with their magic as well). Anything another type of supernatural ability is capable of, an arcane caster can probably do to some degree. BUT...many of them they cannot do as well.
Give arcane casters the most powerful raw area damage effects in the game, since in so many stories it is wizards who throw lightning and fire, cause earthquakes, summon hordes of undead, and so on and so forth. Whatever a given wizard's school of wizardry is, sorcerer's bloodline is, warlock's pact is, that determines the limited pool of abilities they are really good at.
Give other types of supernatural powers less breadth, and more depth. A wizard can heal wounds, imbue others with potent buffs, commune with extraplanar beings, raise the dead, and so on, but a cleric can do so much more potently, and at lower levels.
A wizard can summon animals or storms, can shapeshift into animals, can replenish the land, grow crops, etc, but a druid can do so much better, and at lower levels.
A wizard can read minds, move objects from afar with telekinesis, scry on other locations, but a psychic character will do so considerably more potently, and at much lower levels. While a wizard might be able to speak with someone in brief spurts with a cantrip like Message out of the gate, a telepathic psychic will be able to communicate primarily with just their thoughts if they so desire. A wizard can move objects around with a Mage Hand cantrip right from the beginning of their career, but a telekinetic is already capable of lifting much heavier weights from a much further distance away right at level 1. A wizard might be able to see around a corner with a probe a couple dozen feet away, but a clairsentient instead sends out a full-blown remote sensor, moving it like an astral projection and sensing through it while turning the senses off in their own body, and being able to travel as far as they wish until they turn it off and return their senses to their own body.
I think psionics in general should be extremely focused, a bit more potent, with less numbers of abilities available to a practitioner, but much more ubiquitous in usage. That is to say, while caster types generally have a limited number of uses of various abilities per day, and can mix up what they can do with great utility, a psychic character has far less abilities, but can use just about everything they know at-will, instead using their resources (power points) to temporarily increase the potency of their limited repertoire of abilities.
I have always thought clerics should probably have some sort of different casting mode than arcane casters too, to be honest. Clerics shouldn't be particularly limited to memorizing/preparing a limited suite of abilities, and having a certain number of uses per day. Instead, divine casters should have fairly limited sphere of power their gods hold sway over, and can keep using them as much as they want, but with a further price to pay the more they use it in a day. After all, they're asking for favors from divinity. Favors like that almost always come with a cost of some sort. The more favors you want, the more it will cost you. But that's a discussion for another thread.
But yeah, I think arcane casters should totally have access to telepathy, mind control, telekinesis, clairsentient abilities, remote viewing, etc. And unlike a psychic character, might even have all of those and more at once! But...the psychic characters can use those abilities in perpetuity, and push them into overdrive for limited periods of time with their reservoir of psychic energy.
