still can't improve ctr - what am i missing?

If it worked for two weeks then flattened, check whether the position changed too. CTR follows position, so a ranking drop looks like a CTR problem. If position is steady: rewrite titles to match what people searched (search console query report, look at the exact wording), and check if google is even using your title, it rewrites a lot of them. Also check whether an AI overview or ads started showing above you, that alone knocks CTR down with nothing wrong on your side.