Nowadays intel is not a reference for C++; the versions found on HPC compilers are not the fastest nor the best following the latest standards.
I don't think commercial/open source is the key here: on the fortran side we have been long suffering from a lot of bugs/regressions with the current versions of intel fortran (with respect to the "latest" features like OOP) -- I would even say that they could be more than we are finding in gfortran.
An explanation could be that they are investing time in supporting their big customers that likely use ancient code bases.
Exactly, that is my point: so we are mainly still in the land of Fortran95, which is not designed for taking advantage of the latest features of the hardware.
I don't think commercial/open source is the key here: on the fortran side we have been long suffering from a lot of bugs/regressions with the current versions of intel fortran (with respect to the "latest" features like OOP) -- I would even say that they could be more than we are finding in gfortran.
An explanation could be that they are investing time in supporting their big customers that likely use ancient code bases.