I feel a bit 'meh' about their middle aisles. As you say, get rid of the junk and sell more food. But sometimes there are bargains worth having.
It does appear random, but since shopping regularly for more than six months, you get to see there's some logic and organisation. They do have a lot of things you might go 'erm, do we need a tin of emulsion'? but more often than not they have things like toys before Christmas, exercise stuff in January and so on.
I don't see as many totally crazy products as I used to five or more years ago, when I think they just threw loads of mud at the wall to see what stuck.
I assume the Aldi buyers are quite switched on, and of course they sometimes secure some great deals that go viral and bring people to the shop just for that one item. I've noticed those Reach 'live' sites seem to do loads of ads made to look like articles on how people are going mad for a specific product that saves people money/time etc.
They do need more loose items in produce though. I just take potatoes loose and put them on the belt, but they do sell reusable bags. It's just that, as you say, a lot of stuff is in plastic.