I use grammar as the primary, initial foundation to communicative competency. I only teach privately.
The main problem with grammar is the way it is traditionally organized & taught: separate, isolated chunks as a supplement to content, and using terminology that may not be practical for certain learners (I teach Chinese students).
For example, perfect tenses are all traditionally taught separately (present, past, future). So of course, most students won't understand how they are related & to use them properly.
I strongly suggest analyzing the grammar yourself, reorganizing it, and to teach it "holistically". Start with the 4 basic tenses first.
Clarity is already interesting.