I'm a photographer and yeah, sky replacement is pretty much the bare minimum in terms of processing photos receive. Its not always possible to get a good shot with a good sky at the same time, especially if you're only at a location for a few days. That being said I only have an issue with editing if it is intentionally misrepresenting reality, like making a person thinner or their ass bigger, or something being passed as reality. In the case of sky replacement I would consider it more of an enhancement than an edit. There are sky assets which I'm assuming this is, but many photographers keep a collection of sky images for sky replacements. Timing is always working against you in shots with nature.