You can use the spell to advance the plot and act as exposition
As per the description of Speak with Animals:
The knowledge and awareness of many Beasts is limited by their Intelligence, but at minimum, Beasts can give you information about nearby locations and Monsters, including whatever they can perceive or have perceived within the past day. You might be able to persuade a beast to perform a small favour for you, at the DM's discretion.
It is reasonable to expect the animal to be able to tell you about things it has seen in the last day or locations that are within the immediate locality.
This includes knowing where villages or landmarks are, if anything strange has passed through in the last 24 hours or other things that might have interested the animal.
You, as the DM, would have to tailor this to the animal e.g. birds would have covered a much larger area, and noticed more things, than a spider or toad would have.
This spell could be used to track targets if animals would have seen them, find nearby groups of people or prey, waterways, caves, quite a lot really.
Giving the animals personality and trying to express their motivations would probably be too much as most animals busy themselves with finding food and not getting eaten by something bigger. But both of those things require the animal to be observant to the area around it.