We shouldn't expect the trumpet to correct our unrecognizable pitches, our unfocused tone, or our floozy attacks. However, after some consistent accurate buzzing on the mouthpiece, you can enjoy instant improvement.
(Some argue that buzzing is different than real playing. I agree, but I've always noticed marked improvement after enjoying a good buzz.)
It seems that when it's unclear on the mouthpiece, it's also unclear on the horn. But when it's perfect on the mouthpiece, it's a whole lot better when you add the horn. It's like a ball player swinging two or three bats before stepping to the plate. Don't trust me, or yourself. Trust your mouthpiece.
Assignment: buzz any phrase slowly and accurately with as little fuzz as possible. Don't modulate, and don't approximate. Just nail each note, spot on with ease and no hand pressure. Watch what happens after even a single session of conscientious buzzing! Now, simply add the trumpet, play like you buzzed, and, voila, an amazingly improved sound and focus! Repeat often during your day. Very cool! Your own personal tutor!