In my opinion, the biggest inconvenience with Modern Fortran is that the toolchain is in no way modern. There is no language-level support of a linter, a package manager, a document generator (I use Doxygen but it is not Fortran specific), etc. As a language geared toward numerical computing, I feel that it should have a big standard library that covers advanced math, linear algebra, statistics, ode solvers (like Julia). Yet if you want to get something done, you may still need to reinvent the wheels on top of LAPACK. These things hurt productivity more than the syntactical features.