I'm afraid you are correct.
As you know, those numbers can be improved,
And I do mean can, as you are on the right place for support.
As to 'diet', by diet on here we mean as a way of eating for life, so you need to decide what you can maintain, as you know, if you can't keep at it, it doesn't help long term.
The other thing is not to concentrate on getting the numbers down, too quickly isn't actually good for you, if you've been high for a while, so you need to concentrate on long term, and it'll fall into place.
Lot's of different diets suit. I went on portion control, low GI/lowGL, others LCHF, others are a mixture.
Try what you like, if you like it, that's good, if not, give it a few weeks, and adjust it until you do like it, but you will find after a while. it's a way of life, not a 'diet