Restorative reagents also cures poison and paralyzation. Not having to use a spell slot to cure those conditions is a spell slot available for something else.
Alchemists at that level don't have the same opportunity cost in removing conditions other classes and subclasses have.
They also have healing word and mass healing word for bonus action healing so when it does come up the still have an action the artillerists and battle smiths are lacking.
The cannon gives good damage mitigation bit the alchemist is the better healer with more spell options.
The elixirs are pretty decent for 1st level slots and gives versatility.
Where the subclass suffers is efficiency in using. Elixirs don't have the lasting power of a cannon and neither do bonus action spells looking at spell slot costs.