Spiritual Ally seems to muddy things a bit further, since that showed up in the same book that DID have the Oracle, so it's harder to argue that the language was just because a spontaneous divine caster didn't exist yet. And I just checked, and the Ancestor mystery was actually designed even later, for Ultimate Magic, when it's even harder to argue "never conceived of it" as a reason for the choices.
Does it seem like a weakness of the Ancestor mystery to have two spells that will have poorer attacks than would be likely from a cleric or inquisitor casting it? Absolutely yes, but like Mowgli says, subpar class options aren't exclusive to this. The fixed bonus spells from things like mysteries and bloodlines have
always been a mixed bag. Just from some quick skimming of pfsrd:
What about that super-powerful bonus
Tongues spell that Aberrant sorcerers get as their bonus 7th level? Imperious is stuck with
greater age resistance for heck's sake. Infernal bloodline players get a super useful spell to ... protect them from Good-aligned attacks; super likely to get use in LPF where we don't run evil characters.
I'm not convinced shillelagh is especially useful with the Wood Weapon revelation. And how many animals do we really think Nature oracles are likely to awaken at 2,000gp a pop? They're fine fluff, but are identify, tongues, and legend lore really worth anything else you're getting from the Lore mystery?
Shall we comment on the charm / hold / dominate animal chain's utility for Animal domain clerics? The Healing domain sticks you with four spells you could already cast spontaneously, even though you're already empowering your heals so you wouldn't need as many.
This is probably sounding harsher than I mean it. I'm totally not trying to be. I'm honestly asking the questions, and pointing out that, if our argument is "spell on a bonus fixed list isn't all that useful for the class," then there's a lot of other, similarly not-awesome spells that folks get stuck with that might be worth re-considering.
For what it may or may not be worth: the ability to ignore fixed lists and their concomitant mixed bag is one of the big draws for the
Ancient Lorekeeper archetype, as I understand it. You can qualify for it out of the box with an elf or half-elf, but can also get it via the Racial Heritage feat, which you can use with half-orcs, humans, and aasimar (using the Scion of Humanity alt racial).