These people are accepted by the gullible populace as experts, when all they are doing is producing more science fiction, just like Hollywood. Fabrication. You buy into it willingly, as do many others.
This is simply untrue. You're mixing up two things. Three really.
The first is images which are visualisations - depictions of exoplanets and so on. Those aren't "fabrications". When they mark them as visualisations they're not "admitting" anything. This language implies an attempt at deception. If there was attempt at deception then why would they mark them as visualisations? These things are created to stir the imagination. You're not far off with science fiction, but like much science fiction it's based in reality. They use the data they have about exoplanets and use that to visualise what they might look like. They're not making any claim that they're real photos. And it's certainly not all they are doing.
The second is composite images, or images which have been enhanced. These are real photos, they've just been processed digitally. Like I said, you do this too every time you take a panoramic picture or use your phone's colour balance or cropping tools. This processing is done to make the images clearer, and does not indicate any deception or fakery.
Then there are just photos. There are plenty of those. Sure, the versions you see online are probably compressed and that might mean they have artefacts in, that doesn't mean the originals have been manipulated in any way and NASA have the raw versions on their website.
The scans (not actual photos in the sense of point-and-shoot camera like here on earth) taken from high up are stiched together.
Some are, some aren't. The blue marble is just a photo, taken with a camera on film. The same for earthrise.
The flat map exists.
Does it? Cool. Can you link me to it. The Wiki has multiple maps on it, which one is definitive?
The supposed distances between various points on the earth are extrapolated only from the given travel times.
This is incorrect. Travel times are a reasonable proxy for distance, but you can use Google Maps to find the distance between places and compare it with measurements you take mistake. There's a reason that as you zoom out the curve of the earth is now shown. Before that the world was extensively surveyed. There's a whole field of geodetic surveying which takes the earth's curve in to account.
The actual straight-line distances are not known as they are not able to be taken due to the methods used for long-distance travel where waypoints are not visible at ground level.
Also not true. It hasn't been true for centuries since Harrison cracked the problem of accurate timepieces at sea - using those and combining it with celestial observations meant that ships knew where they were. And it's definitely not true in the era of GPS.
The routes taken are the routes based on the celestial sphere routes that have transcribed down to the flat earth plane, routed by the star patterns overhead.
This is just incorrect. They're based on the great circle route between those two points.
There is no distortion on any useful travel map.
Right. Because travel maps generally deal with a very small portion of the world. Which brings us back to where we started. You can't tell the shape of the earth just by looking around and thinking "looks flat". Any more than you can look at your hand and declare there are no germs on it because you can't see them. For objects which are too big or too small to observe directly in normal circumstances "alternative evidence" is required.