If a viewer is left assuming Palpatine and Snoke were the same or mostly the same character, then their view of TLJ is harmed, as to them ‘killing’ Snoke would mostly ammount to unplugging Palpatine from a host body.
Funnily enough, I actually find this enhances my enjoyment of TLJ rather than harming it. Yes, I understand it retroactively isn’t as much of an impactful event because he isn’t the “big bad” of the trilogy anymore. But when you have such a powerful villain die so easily in the second movie of a trilogy, it is to be expected that he would be diminished in such a way. Otherwise, the final movie in the trilogy has less stakes than the second one. That’s just bad storytelling in a trilogy.
With the removal of all the Snoke bodies he could easily be perceived not just as one of many potential host bodies, but as the only host body Palpatine had at his disposal that wasn’t attached to a medical crane arm. This in and of itself is significant enough for the characters to have defeated in the second movie. At least for me.
I’m not saying that moment is harmed because Snoke is no longer the big bad, he wasn’t by the end of TLJ either and whether he was a puppet or not wouldn’t change that. I’m saying it totally negates Kylo’s whole character arc in TLJ if all it amounts to is pulling the chord on a Palpy puppet. If we have some degree of separation between Snoke and Palps at least the story in TLJ is only harmed by bringing in another big bad, instead of it being literally the same one, thus negating the conclusion in the previous movie.