Can we ban, "I'm not trying to (blank), but" from the English language?
Just be honest and say you are trying to do exactly that
Don't take this personally, but...
Don't take this personally, but that's a bad take.
Unfortunately, these disclaimers are often necessary, especially online where tone can be hard to detect. Yes, it will be followed up with some non-positive feedback, but it also shows the willingness of the person to remain objective and unemotional in the follow up conversation. But they actually have to follow through with that.
Personally, I often find myself avoiding giving constructive feedback because it's tricky to do it respectfully, especially in writing.