That's just how it is, my 1997 Land Cruiser had the same fluid in the gearbox until ~300000km last year when I changed it the first time, which is beyond the mileage where most cars around here get discarded.

It does not make it any worse.

Like with this grease, some guy even said it should be swapped yearly. You're not doing anything good by that - if anything you're most likely to harm something like strip threads to some panel or whatever. Gears don't require a lot of lube anyway, it's probably more important for the bearings that drive them.

These kitchen aid mixers also probably use sealed bearings in the electric motor and most people don't think about repacking those with grease.