"Power" is relative in this. If power means outcome, you can get outcomes in life even by wrong means that will cost you way more than what you get. In all examples, this comes with serious downsides, that costs you way more later.
You can get 1 million loan, pretend for a reason to be rich, squander everything, then have to pay interest and who knows what or be destroyed by loan sharks if you took a loan from bad sources you could not sustain.
Then they flex, they go pretend they have power for a season, and like a deck of cards, they eventually collapse. All good they think, but it's for a season.
Some people can get it from a loan-shark, you can speak to a loan-shark. What the loan-shark will never do however, is teach you how to generate your own; they want you indebted and a fool.
Then the loan-sharks come for their due; payments, beatings, enslavement, psychic damages, and your life can be ruined in an instant. Typically, things "received" are taken on factors multiples by the tens of times, and suffering hits them worse than anything; especially in their later years or consecutive lifetimes.
You can at the same time get a healthy loan, and co-work so you grow healthily your finances.
Or you can learn how it really works out for you, accept where you are, not engage in nonsense, and live a healthy balanced life that grows in accordance to your means. In this path you learn and you can overcome all the loansharks with patience and resolve, or you won't need them.
The practitioners who just summon whatever, don't know terms, they have no idea, and they engage anything, might get any outcome. The outcome is temporary, and their soul pays the bill. Their favors can run out, then they have to pay way more than they received.
They also don't know WHY anything occurred, HOW they can stop it, or HOW to manage it, or HOW to grow it. They must go to the astral-loan shark again, to request more; at costs they can't manage or can't even know. It's futile circle like drugs. As thus their power lasts for a season only. All these "witches" who do whatever and have no clue, live either terrible lives, or experience tragic reincarnations because of all their pending "deals".
Godhead is the situation where these powers come from within and on proper terms, from your power, by the Gods who legitimately teach you the know-how and all the things loan shark entities do not. You ARE the power, you BECOME it.
These "practicioners" you cite, they are NOT the power, they are using something else's power; so they are at it's mercy. A powerful Zevist with a track record can easily overcome or dismantle them in a 2 hour timeframe. They never reach true power and true wisdom, which takes time. They are fake kings with a borrowed tin crown.
After you grow yes, you can do everything they could do, and beyond, without however having to owe extensive favors to things you don't even understand. You can 1-shot spells, 1-shot succeed etc, with your own power and knowledge you have gained from Zevism.
This however, builds on the foundation one has built.
On their side, it depends on the astral cartels they work with, which bless them nor with freedom, nor with personal knowledge, nor with power, but dependency and in many cases, ignorance.