Hands off, he's mine!

People have to remember it is live music and they often have to sing songs that are not ideal for them, sometimes in a different language, and change the arrangement to suit the dancing.

Some people complain that their versions of songs are not as good as the originals. Go to a live concert and see how close the original performer can get to the 'original' recording ( which had been doctored in the sound studio to perfect it - a bit like airbrushing a model's photo ).

Overall they do a high quality job.

The thing to remember in this day and age is that Dave can have the pick of the session musicians available. There's far more of these sort of musicians available than there are jobs to go round.
The other day I spoke to a 25 year, time served tenor saxophone player from Liverpool who went to the Royal School of Music, I think he said.
There were no jobs he said, available in Liverpool, so he was reduced to busking outside a shop in a suburb of Manchester. He was brilliant (and collected a few bob too).

At one time the BBC used to support all sorts of bands and orchestras, regional ones too.
I think there's only one full time band now that they retain.

An in joke amongst musicians is; "How do you tell a profesional musician's car? It's the one with the pizza delivery sign on the top."

It can't get any better than it is, given the constraints enforced by the producers and the sometimes rubbish choices of music.
Dave Arch could probably choose another ten sets of musicians and they'd sound pretty much the same as these.