I don't like shiney engines, I think they have ruined that part of the restoration. Old paint is part of an old engine, and should be kept, IMHO. I by far prefer to see an original engine, and find shiney examples unreal and boring.
Trolleys are a farce too - usually completely out of character with an engine, horrible varnished timber, as if it were a piece of furniture, or RHS steel and welding, completely out of character with the era.
Naturally there are problem engines - my Crossley had been slathered with blue paint over every single part, a repaint was the only solution.
An unrestored tractor or engine speaks for itself, it shows its age with its patina. A repaint removes all that component and makes the engine a foreigner in a new era.
I think the "strip it and paint it" reaction is normal to all who like to see machinery bought back to life, but I think we need to re-think this one, and consider the paint as part of the machine built so long ago, and worthy of preservation along with all the other parts.