I never thought of it that way and I do agree that Shepard and coopmaster need more unique uses but I feel the rancher path also needs to rival artisan more. while not being the animal Profession artisan is typicaly the more profitable profession for animals. Prehaps separating animal and artisan goods along with Increasing the base price of certain later game animal products like goat cheese and duck mayonnaise/feathers could help support an late game animal farm without pigs.
Honestly there are so many factors that could be changed
1. First off, coopmaster/shephard already do a lot while tiller/artisan are super basic, if they got some variety instead of insane stat increases (in the case of artisan), to match even agriculturist it would be nice (I can think of a bunch of ways this could be done really well, it's just hard to make a change that won't upset what players are used to, even if objectively better)
2. Your point about animal products is a good one, they're simply inherently pretty bad for the startup cost of the buildings they use. It really shouldn't be a competition for g per tile for a building vs some crops you can slap down when 15 tiles worth of coop takes 10s of thousands of g and thousands of materials to make, let alone populate with animals