The Dark Naaru element often gets brought up to try and shutdown that line of logic, but there's a few reasons why that argument fails.
Racial leaders are special - It's the same argument that some people used when Void Elves were first introduced, to explain why Alleria can look as she does and player Void Elves could not. This argument can cut both ways though. Alleria is far more powerful than any player Void Elf will ever be (as most racial leaders are). This could be because of the powerful void entities she's consumed, but we have very little information regarding what is or is not
required to follow Alleria's path to power. In the quest
A Vessel Made Ready, Locus Walker says:
After some consideration, I have decided to allow Alleria another opportunity to pursue her destiny.
I suppose you want to know what that means, mortal.
<Locus Walker laughs.>
Meet us deep in the Shadowguard camp ahead-
my brethren are preparing a summons that will provide adequate energy for Windrunner to begin again.
Witness what happens when you harness the Void's power.
This implies that only "adequate energy" is
required to follow Alleria's path, not specific types of void entities. "Adequate energy" could likely come from a variety of sources, with Nhal'athoth and L'ura just being conveniently accessible. Telogrus itself is steeped in Void Energy as indicated by the Void Elf unlock scenario text, and the void storms that still linger in the zone after Void Elves are unlocked. This seems to indicate that it may be an ideal place to harvest void energy, whether from the void storms themselves or by summoning powerful void creatures to draw "adequate energy" from. There's nothing in the lore or the game text that indicates that a Dark Naaru, or any specific type of void-infused entity, is
required to harness the void as Alleria did.
And since players are typically never as powerful as their racial leaders, and can't do many of the things their racial leader can do, it's kind of unfair to expect that they follow the exact same path to their own power as their racial leader did, or at least they are at a point in their process that is further behind their racial leader. Consider Alleria a master and player Void Elves as novices. It wouldn't be logical to expect the novices to have consumed a Dark Naaru before beginning their career with the void. Alleria certainly had void powers long before her Argus story arc.