I enter monthly club photo competitions. When you view the entries, you have no idea what type of camera was used, the settings, the lens etc. Yet I know that other photos are taken with a mixture of FF and APS-C cameras. There's even the occasional film camera and P & S. But usually its almost impossible to tell what type of camera was used. And in 100% of cases, from a viewer's perspective, it is irrelevant, because you are only interested in the final result. You're more concerned with impact, emotion, etc.
But from the photographers perspective, choice of camera is very relevant. If your final result relates to an image in low light, fast action, taken in the rain, needs particular lenses, etc then things are so much easier if you are using the right tool for the job. Given that FF cameras have traditionally been more feature packed, apart from IQ, there are a lot of other reasons why they might be the best choice for someone. Just as in many situations, a crop camera is the best choice.
In summary - when viewing the final result, nobody cares what camera you used. But choosing the right camera makes it easier to get the best final result.