Uh... What?
Once you remove how they function in combat, there's like... three different possibilities. Something that flies. Something that swims. None of the above.
Why are you removing the many possible combat applications for "creature on demand"? Are they so trivial as to be just not even worth mentioning alongside the non-combat stuff?
As for "like... three different possibilities" holy cow... your games are way different than mine.
The big draw for "dial-a-feature" utility includes the vast array of various animal abilities you may need for your group...
Something with darkvision
something with blindsight
something with tunneling/burrow
something with advantage on checks involving smell for tracking.
something with high strength and tons of carry capacity
thats just a few off the top of my "swiss-army-wonder-varmint" head - in addition to that whole you know combat option thing.
I get why druids would want it to be their go-to for all , just like druids would love to have an absolute memory of every varmints ever seen for wild shape instead of limits too. that whole buffet line of "tool-on-demand" is very tempting. Nevermind its out of whack for a third level spell when compared to similar spells that do a small fraction of it.
its cases like this where "player agency" gets really degraded IMO as it gets turned from "aggressively countering player's power to control their character and determine or influece direction and results" by smooshing into it "Gm limit's character's power to match the other benchmarks".
But hey, i am sure a "good enough GM" can roll with the player agency of the dragon-slayer darts at 1st level too and not infringe on their player's agency.