I care a lot about sightlines, I'm mostly interested in themed environments and immersion. I think of sightline issues in a theme park as varying in negative impact in terms of how much they take you out of the fantasy. A grade can be given to a park, a land, a specific queue, a dining area or stretch of walkway, etc.. So there can be Grade A lands in a park that overall would be Grade D.
Grade A -- Guests are fully immersed and cannot see any intrusions that break the fantasy.
Grade B -- Guests can see thematic elements from other lands/themes (e.g., seeing Matterhorn from Frontierland).
Grade C -- Guests can see designed portions of on-property yet non-park amenities, such as seeing the portions of a park-integrated/adjacent hotel or retail that are designed -- detailed, embellished, decorated -- to be seen by guests.
Grade D -- Guests can see any backstage or non-designed portions of on-property yet non-park amenities (e.g., show buildings, backside of a hotel, parking garage, transportation system).
Grade F -- Guests can see off-property elements (e.g., unrelated office buildings, hotels, transmission lines/towers).
I imagine some theme park fans don't care about any of this, or just care about Grade D or F intrusions, it's really individual. And while no intrusion -- not even a Grade F park like Disney Califoirnia Adventure -- would keep me from having fun, I do really appreciate the effort and cleverness when theme park designers deliver a Grade A experience.