Not necessarily. In the general case, restrictions can make a language more powerful [1], by allowing the user and the compiler to make more assumptions. E.g. removing gotos and mutations seem good ideas.
In the case of C vs C++, removing operator overloading and exceptions could turn out to make the language more powerful.
[1] If you use the right definition of `powerful'. You need a sensible definition that avoids "They are all Turing complete and thus equally powerful."
