but you can also use it, if you aren't a spellcaster, to help a spellcaster land that critical spell. It won't happen often - maybe once a day

- but it can be clutch.
The problem with this logic is that
nearly anything CAN be clutch.
Hunter's mark "can" be clutch--you do
just enough extra damage to kill something that would've pasted a friend. Even weird obscure spells can be clutch in weird obscure situations. When the standard is met by every spell, it's not a very useful standard for separating spells from one another.
Is it
useful? Yes. Being able to have a high chance of negating one critical hit a day is decent--not amazing, but decent. I don't think that specific benefit is unequivocally better than other spells you could get via Fey Touched. The advantage to an ally is similarly useful but not amazing, since you're very limited in how you can strategize around it, being unable to save it for a preferred roll. (E.g., even if you give it to your Wizard friend who's preparing to cast a clutch spell, said Wizard cannot choose to hold onto it when the enemy casts
fireball at her before her turn comes up. She
has to use the Advantage on the
next roll, even if it isn't her preference to do so.)
Silvery barbs is a very good spell, an upper tier 1st-level option. That it can be acquired via Fey Touched surely does make FT better, particularly since it doesn't depend on your casting modifier (and thus it doesn't matter if you increased your preferred stat with FT or not). But is it enough to make FT unequivocally insanely amazing? Ehhh...not sure on that one. E.g., I still think a Dragon Sorcerer would favor Elemental Adept for their chosen element first, Lucky remains a ridiculously powerful feat for any character, and Warcaster remains vital to any spellcasting character who expects to make Concentration saves. As others have noted, the biggest benefits of
silvery barbs are for characters who have plenty of extra 1st-level slots to burn, and that doesn't apply to non-casters,
particularly since there may actually be times where a melee character would want to use
fey step instead of
silvery barbs, but you're only able to cast one of the two spells each day.