If you want simplicity amongst the noise - follow these guidelines.
If it doesn't grow and it doesn't move (when alive) - don't eat it.
So vegetable, fruit, meat, fish, seeds/nuts - all good.
Anything that comes in a packet and has a name on the ingrediants that you can't pronounce or you wouldn't find in a average kitchen - don't eat it.
Anything that has been mildly processed (foods that people processed 500-1000yrs+ ago) - cheese, milk, yoghurt, grains, oats, bread - eat moderately.
Follow those rules and you're eating a healthy diet.
If you want to put it in a woo/hippy type way - Eat what the earth provides that requires minimal processing or processing that you could technically do in your own kitchen if someone showed you how (like making cheese/yoghurt/bread).
If you can pick it or pull it and eat it straight away - it's good for you.
If you can kill it with one cut, cook it and eat it straight away - it's probably good for you.
If you have to take it away and process it into something else (grains) - it can be good for you, but bare in mind how long and labour intensive the process would take to do that - therefore don't eat loads of it. Those foods have been designed to add bulk calories (energy) for people who needed them. For example, bread 500yrs ago was closer to rye bread - dark and dense with thousands of calories and it supported people getting through long arduous and freezing cold winters. In our centrally heated homes, we don't need to be eating lots of bread now.
Anything that advertises itself as 'healthy' - step away. Healthy foods don't need advertisements.
Things that can trip you into making mistakes is looking at highly processed meats - bacon/sausages. You think they're meat so they're ok - but they are processed/smoked/mixed with fillers. So check the back of the packet for those unpronounceable ingrediants.
If you're not preparing it and cooking it with your own hands (you're just putting it in an over) - proceed with caution and check the packet.