It's great to hear that this little piece of technology inspired amazement. It is quite something.
Your observations is spot on:
Indeed, the environment is far from ideal. 2-3 years ago dentists had to apply a powder onto the patients teeth to make just the scan of the teeth work. Now the software has matured to work powderless. The scan has to work for a wide variety of surfaces and vis-a-vis refractive indices like teeth, metal implants, ceramic or gold inlays, gingiva, orthodontic engagers. The very high end models even detect tooth decay / caries.
The stitching is another challenge. Again, in the past the scanner would loose his reference on the mouth and it was fiddly to get it back to continue from the last scanned part. The team working on this was brilliant to overcome this problem and now it is a smooth experience
Finally, accuracy is something all devices on the market having a hard time with. They are operating on the limit of what is possible. Small partial scans are no problem. But when you scan a full arch, you must ensure the deviation does not exceed 30-50 microns over that full arch. Otherwise, if the dentist plans to do a big bridge that spans several teeth a lower accuracy will lead to miniscule deviations and twists in the designed and later produced bridge, that the patient will recognize it and feels that it "just does not fit right".
Our mouth is super sensitive in this regard because of the high number of nerves/sensors. Our tongue operates like a magnifying glass. When you have a small hair in your mouth or between your teeth you will feel that right away.