Since this seems to be the place for personal views, my views, after 20 years of experience, is that people do not notice the complexity of anything that they have digested as normal. As a result doing anything other than what they are used to seems very complex to them. Whether that other thing is actually complex to a neutral third party is situation and observer dependent.
I have seen this with procedural programmers struggling with OO code. OO programmers struggling with functional techniques. Programmers of all kinds seeing a new framework. Programmers used to more structured code trying to fix shell scripts. React developers encountering code using older JS libraries, and developers comfortable with older libraries encountering React. And so on and so forth.
In all cases the common denominator is that the programmer is uncomfortable with the new way of doing things. And the first reaction is, "What's wrong with this code?" And "It's messy and complex" is one of the easiest conclusions to draw.
I have seen this with procedural programmers struggling with OO code. OO programmers struggling with functional techniques. Programmers of all kinds seeing a new framework. Programmers used to more structured code trying to fix shell scripts. React developers encountering code using older JS libraries, and developers comfortable with older libraries encountering React. And so on and so forth.
In all cases the common denominator is that the programmer is uncomfortable with the new way of doing things. And the first reaction is, "What's wrong with this code?" And "It's messy and complex" is one of the easiest conclusions to draw.