Anyone that can't get a good shave out of a Tech needs to work on their technique, specifically learning to hold the razor at the correct angle for the entire shave and their beard growth pattern.
Yes Techs are "mild", yes they have a narrow sweet spot, yes it may take you three passes and a touch up pass to get a BBS/DFS but no, your beard is not too "tough" or "coarse" for a Tech; they were sold and used for over 40 years for a reason by people with gnarlier beards.
Techs are the best starter razors as they teach the fundamentals of DE shaving correctly and well. Learning how to use a Tech will improve your overall technique with DEs and will improve your shaves with more "aggressive" razors.
Couldn't have said it better.