Like every Product, there is a price-functionality curve, and while it is true that some big ECAD software have capabilities beyond what Eagle or Kicad offer (see other answers), those capabilities are often either very niche or very high level, and thus not needed for most applications.
Kicad and Eagle both have the advantage of being free (under certain conditions for Eagle), so of course hobbyists will use those, but having a low entry cost does not mean that the ceiling of what can be achieved is low too.
I have worked both with so-called "hobbyist" and "big boy/professional" ECAD software, and in both cases, I did not choose the tool, I had to work with what the company was already using and adapt to that. When I had to procure my own software for a customer, I went with Kicad without hesitation.
On top of that, and like every software out there, some people tend to be opinionated about their habits/choice of tools, and defend them with less than perfectly objective arguments.
In conclusion, the software itself matters far less than the skill and knowledge of the designer using it, and I would be wary of anyone trying to belittle a design solely based on the software that was used.