Lol, it's a dealer's service thing - period. Regardless of under which brand name.
My sis's BMW dealer, the largest one in Montreal area - only employs mechanics fresh out of mech. schools. Want to discuss the quality of service - or rather - the quality of work?
At 40k km we discovered that the dealer has never changed the factory - installed oil filter. A simple oil change procedure has been turned into a full blown toomba-yaa, teeth-removal-through-ones-arse dance with special tools and having to drop the whole bottom engine's covers. So even Toyota's techs didn't feel like it.
Ya, bad experiences aren't confined just to Mazda dealers.
I've had bad experiences with a Ford and a Honda dealership, just to name 2.
It seems that so much depends on the management of said dealership. If you find a good one, stay with it.
I've had several Nissans, and had a really good dealership where I went, even for post warranty work. Good service and good people.
A few years ago, they sold the dealership to a conglomerate, and it went in the dumpster soon after that.
Lots of changes (for the worse), almost all new staff (for the worse), and now they are struggling (no surprise). I don't go there anymore.
I haven't had to use my local Mazda dealership yet, so it remains to be seen how good or how bad they are. I guess I'll find out some day.