Most people would not tolerate pure myrrh by itself. As someone has posted, it comes from the sap of a tree, and in “solo” form is often fairly large irregular lumps. It burns/melts with a very sharp, acrid odor that burns the nose. It was used in embalming, and is a bacteriostatic substance. It smells “mediciney”. Use in the pure form is a sure way to have folks in the congregation coughing, choking, and gagging, and complaining about having their allergies unnecessarily inflamed.
Frankincense, in its pure form, is also a sap. It does have some sweetnes to its odor, which myrrh does not. But, in pure form, it, too, can smell strong and irritating, and will frequently smell like strong pine resin burning. Kinds like a forest fire. Again, in pure form, something that most congregations would not tolerate unless they were doing penance.
Most incense that is tolerated by congregations may have SOME myrrh, and/or SOME frankincense in it, but not in the pure form, and not without other aromatic woods and saps being added to ameliorate the irritation, and to provide sweetness to the overall odor.
The incenses used by Eastern churches often are sweeter than what is more frequently used in Western churches. Their monasteries and suppliers developed different habits and customs, as well as natural variations caused by what natural substances were readily available in their regions.
I have found congregations generally to be much more tolerant of the sweeter, less aromatic/pungent varieties, such as Damascus Rose, and seversl of the ones with flower-baser fragrances added to the mix.