Interacting with intangible beings isn't the problem Lancelot is facing in R2.
So... we are going to ignore that Medusa was literally sucking away someone's Soul in UBW? Does this dumbass even realize Magical Energy from a person come's from their
SOUL right?
If you decide to look up edo tensei in action you'd notice how they don't have an intangible ghost body that's serving as the source of the regeneration. They just regenerate ex nihilo* and keep going.
Which is done by Chakra which is why something that can negate Ninjutsu can ultimately destroy it despite the Soul still existing... which Noble Phantasms and even Magic Resistance has done for far less.
Lancelot has nothing in his arsenal besides soul-eating that could be used to permanently kill an Edo Tensei zombie.
Nope, Noble Phantasms and enough Magical Energy can explicitly fuck with Spirits of even a high grade. Magic Resistance can most definitely undo Edo Tensei as well so he has 3 ways to kill an Edo Tensei.
As the soul-eating is not a viable combat applicable technique.
Again, completely wrong as Medusa herself shows, let alone any Servant worth a piss. He keeps thinking it's some elaborate technique when for Medusa, it's literally just biting her victim and for most Servants, it's just attacking them with a decent enough Noble Phantasm.
There is nothing he can do against the Edo-tensei besides retreat and concede. Or run out of mana and die. Even if physically dismantling them via buzzsword to the face is well within his capabilities. And if their souls were to manifest outside their bodies he could do the same to them. But
Acting as if any of the Edo Tensei are a threat to Lancelot when a Numerals Gawain isn't is just laughable as fuck.
1. Naruto souls don't work like that as we see by their interactions with the Rinnegan. As far as I know (maybe Boruto changes this.) actual spoopy ghosts just aren't a thing. Even chakra apparitions like Minato and Kushina inside the Nine-tails seal visually had a physical form and IIRC physically interacted with Naruto rather than being intangible.
So this dumbass realize that this is the same for Nasuverse Souls right? Hell, Nasuverse Souls are even more bullshit than Naruto Souls are at their core concept and trying to go "Well there is only Chakra Apparitions and no actual ghosts" as if that boosts Naruto up is fucking insanity. All that further shows is that Lancelot would barrel over everyone because a decent enough attack WILL affect their souls straight up. But that's only his dumbass take and not the actual fact that Naruto Souls are affected by Chakra meaning yes, Medusa can soul suck people's souls and so can Noble Phantasms affect their Souls.
2. Naruto souls, as we see during their interactions with the Rinnegan, do not require enhanced senses to see. Yet anytime an edo tensei regenerates. Their soul is nowhere to be seen.
Their Soul still exists within the Edo Tensei which we know when Hiruzen LITERALLY PULLS OUT THE SOULS OF HASHIRAMA AND TOBIRAMA IN HIS FIGHT WITH OROCHIMARU! How you think they ended up in the Shinigami in the 4th Great Ninja War Arc?!
Lancelot's ability to hurt ghosts is irrelivent because he isn't facing any. If anything he's closer to fighting zombies or maybe even a kind of paper golems. both of which servants fight on the regular in FGO and as far as I know "nom nom nom souls" is not considered a viable method of dealing with them.
OMFG, we are just going to pretend that he can't effect the Edo Tensei souls with completely lying about how the shit works and ignoring that the Souls are explicitly in the Edo Tensei bodies and that Servants somehow cannot attack Souls directly despite the fact they can and do so. It's like this fucker can't wrap his head around the fact that Nasuverse Souls are stronger than Naruto's which is why it's difficult to do so without being that much stronger which is why a normal ass high school girl can survive a Soul Suck for a minute but Orochimaru has to struggle with a dying man to avoid his being taken out.