It can be quite pricey and there is no lifetime option if you want to but a membership, but it would be worth checking out (at least to me). But SoD is exactly like star stable but with dragons. Horse Ranch has breeding, the ability to catch wild horses (and maybe even a unicorn or two), events, open-world exploration, etc.
Not to mention you can do all of this for free! This game doesn't have the best graphics in the world, but it has a very large open world, clubs, the ability to catch wild horses, the ability to keep 100+ horses (with crafting barns), crafting, character personalization, horse breeding, auction house, racing, events, etc.Here are some games that I enjoy/enjoyed playing whenever Star Stable gets a little boring