I don't recall anyone being "objectively-sucks" level of unhappy with proprietary C compilers. Moving to gcc was often a regression -- because it was much slower to run and sometimes generated worse code -- for developers used to Turbo C or CodeWarrior-style IDEs.
AFAIK when it comes to using the features of recent CPU architectures, Intel's compilers produce more performant / efficient code than GCC or Clang.
A sufficiently smart compiler requires ever more clever compiler writers who are deeply knowledgeable about the many quirks of the numerous architectures.
