Thank you @gnikit !
Yeah, exactly, I looked at the settings in modern Fortran extension, it seems to be a one size fits all solution.
The only reason I installed the Fortran intellisense is that it can show the variable/subroutine/functions properties/informtaion when my mouse hover on them (like Intel Fortran + Visual Studio does), for example, when I put my mouse on a subroutine of mine called mydiffeq_init, the intellisense shows the information of my subroutine as below,
Without Fortran intellisense, I am not very sure if such information can still be displayed. But one of the drawback of Fortran intellisense is that it requires installing fortran-language-server using pip, and sometimes it cannot find the installed fortls.exe, and I have to manually set it in the extension settings.