Well to be honest, Vegeta hard counters both Luffy and Naruto. While they would still have Chakra and Haki, Naruto would lose Kurama, the powers of the other Eight Tailed Beasts, the 6oSP powers, and Sage Mode. Similarly, due to the spiritualistic nature of Devil Fruits, (and the fact it is an external power up given to him), Vegeta can separate it from him and nerf them. They're, by DEFINITION, what Forced Spirit Fission can undo.
Ichigo is immune due to the sole fact that while his power ups work through external means, they're actually 100% from an internal source. They basically use a middle man. Whether that be Rukia, his false Bankai, etc. They come from him but are harnessed through external forces that would make you think he'd be vulnerable. However, once Naruto and Luffy are gone it's Ichigo by himself versus Goku and Vegeta, who have much more combat experience and can get around him with illusions, teleportation, auto dodging, their pseudo-precog, sealing, paralysis, deconstruction, etc.
This is also ignoring that throughout the fight, even without technique and transformation multipliers, (such as Kaioken, or in the case of the Big 3/HST, things like Blut Vene, Boil Release, or Armament Haki), Goku and Vegeta passively grow in power through combat. Like, Vegeta taking a hit boosts his power above them, and with equal stamina he'd swiftly outgrow Ichigo even if they can't nail him with any of their hax options, allowing them to kill them with a good ol' fashioned punch to the schnoz.
That said, before Moro and the Granolah Arcs, I think there's a case to be made that the HST could have won (in a stat equal). They'd have all their hax, which gives them precog (which only would have been countered by their predictions, and raw future vision is better than that), cellular level attacks, turning people into frog statues, corrosion, etc.