That is not the issue... The problem was Bethesda making an official sequel instead of a spin-off game —but a spin-off is what they produced; and as you can guess... for their existing fans. This action was effectively the same as if Nintendo had acquired the Elder Scrolls or Halo franchise, and made
their TES-5 or Halo-6 a Mario Kart clone—or whatever else they considered popular at the time. It is an unrelated experience. There is fun, and there is fun; but not all fun is interchangeable. There is such a thing as the wrong kind of fun—for the situation.
Bethesda chose to re-skin their TES franchise with the gutted pelt of the Fallout IP; so they could sell TES twice.
If these were films and not games... it'd be like making a 'Lethal Weapon 5'—starring Patrick Stewart and Ian McKellan as bio-terrorists, in a not-funny drama/horror film. IE. The only things remotely similar are the names... IE. No one who would seek out a sequel to the previous film/ or game, would be looking for that kind of an experience. The problem is that modern developers don't tend to care about making an experience appropriate for the product's name.
IE. It does not matter who thinks what is fun... it matters when one sells the fun labeled as a different kind of fun than it is. IE. (again
) Something called 'New and improved Vegemite' should not taste like strawberries & cream, no matter how popular (or preferred) that flavor is. Fallout is like Vegemite, where FO3 is like Nutella.
Nutella and Vegemite look the same, but are offering entirely unrelated and dissimilar flavors.
Not unlike Fallout and TES.
FO3 was TES in Fallout costume—not a proper Fallout follow-up title to permanently occupy the #3 slot in the series; it was one that offers nothing of the series except for a few cherry picked nouns.