1. Players who only play one instrument, albeit play it well, insisting on playing in every piece. Changing instrumentation does wonders.
2. A split between selfies and trad - do both, and develop your own sound.
3. Excessive aspiration to be a top band making everyone sound like them.
4. The ubiquitous guitar - sorry, but it has to be said the guitar is not a trad instrument, it was the 19th century equivalent of the pukelele, easily accessible. Just because it was crossed over from C&W in the 1960s with the American school doesn't make it right, it pushes the sound in a "wrong" direction. Have some, fine, but not the whole ruddy time.
5. It's time to question whether the GHB has a place: the Bagpipe Society has fairly conclusively shown it did not exist before 1790, making it an invention of the British Army, and so playing 18th century pieces on it is just plain wrong. That does not, however, apply to the other small and chamber pipes, which in addition have a far more conventional scale.