Interacting with them is a royal pain in the butt. I want to feed my horse an apple, and the sims and horse spend like 30 ingame minutes messing around, positioning themselves in a way that the game finds acceptable for the interaction to take place. Then I want to pet my horse immediately afterwards, and both sim and horse have to reposition themselves AGAIN even though they're in the middle of a wide open goddarn field, usually with the horse needing to walk around in a circle for whatever reason.

Please tell me I am not the only person who has noticed this... and please tell me there is a way to fix it?

I'm sure you are not the only person with this problem but I have not seen it too often. There are probably other factors within your game contributing to the behaviour you are experiencing. Your game could be a bit overtaxed. Does this happen in all worlds? On all lots? There are some steps you can take to clean up a bit so things run more smoothly. Are you using any mods that clean up for you nightly such as NRaas Overwatch and Error Trap? Those would help. Have you tried resetting your town? Here are some tips for Better Game Performance that might help you out.

Oh, yes, I've had this issue as of late and really I can't think of anyway to fix it besides making them do the interaction again or moving them.