The word BUT negates all the goodwill that you are building up with the first part of your sentence. The BUT gets someone’s defenses up, and makes them way less able to hear the important thing you want them to listen to. Instead, using the words AT THE SAME TIME or AND can be much more effective. This keeps both viewpoints as valid.
– “It’s great how you do [that] AT THE SAME TIME, I am hoping that you can add [this other thing].”
– “I agree with a lot of what you are saying AND I wonder if we could examine this particular point.”