MTG Salvation

That is a really good sideboard card that we could be seeing a lot of if the metagame skews towards artifacts (which is possible given the good additions in M20) or high-value enchantments (e.g. Frenzy).

Not as good as Disenchant/Naturalize. Usually lifegain isn't worth going from two mana to three, considering you usually "cast removal and do something else".

I would agree with you, that this is worse in a control meta but there have been a lot of metas with fast decks against which this card would have certainly be useful as a sideboard option--for example, this card would have been used in the Experimental Frenzy burn meta or against Kaladesh's Heart of Kiran aggro decks as a way to remove a key threat and extend the clock so that you can gain board control.