In all my years of coaching, I've found three things to be commonly true:
Most people know the difference between healthy/helpful foods and those that aren't.
Most people have negative or unhelpful beliefs about food.
Most people only have limited options when it comes to food preparation.
Why are these things important?
Firstly, the good news is that you probably already have a good idea of where you're currently at, nutritionally speaking.
Secondly, much of the information that's preventing you from progressing is flawed or mis-represented.
Lastly, if you've tried to eat healthy before and couldn't sustain it, it's probably because cooking, creating flavour profiles and the mouth feel of certain foods weren't part of your plan.
For example, lets say your preferred flavour profile for a main meal is highly seasoned. If you try and get by on steamed chicken and brocolli, it'll get real miserable, real quick.
Sounds obvious right?
Try this. Lets say you learn that you prefer the way a particular food 'feels' when you eat it. If you don't know what your preferences are, no off the shelf approach is likely to work.
Just to be clear, there's nothing magical about this. I'm not releasing a mouth feel diet. But it is a reason that certain foods can be more palatable to some people than others.
So that's the kind of thing that gets addressed practically. The technical side is essential for determining a starting point, but the practical is what tailors it to you as an individual.