Only reason duct tape doesnt hold anymore is because american companies
are tightassed profit driven outfits who over the years have just made
their products cheaper by cutting back on quality. I know whole
subdivisions with duct joints sealed with gray cloth duct tape that are
still stuck after 25 years.

Yes...nowadays its best to use mastic tape....dont use the thin
foil....it lasts about as long as the cloth tape used today....