The only thing the gearery can't do is anything but make iron gear wheels!
If you want to produce iron gear wheels, though, that's what the gearery is for. It has a crafting speed of 2.5 and a +50% productivity bonus (changeable in settings), so it is very good at its job. It may get more use without Space Age, but it is useful even in Space Age games before you have access to the foundry.
Normally, you can only make gears from iron plates, but if you enable expanded recipes, then you'll have a lot more options... the gearery only makes iron gear wheels, but that doesn't mean it can't increase the variety of what you can make iron gear wheels out of.
This mod integrates well with Iridescent Industry but can also be used standalone.