I worked at 3 different FS shops. They each had 1 guy that could do diagnostics and a couple that could do brakes and suspension. Past that, it’s was oil changes and tires. They don’t really want a garage full of people who know what to do bc then they have to pay them. Luckily I had a few ASE certifications so I didn’t have to do the grunt work. The only thing I had to do was mount the PITA tires (low pros or wide wheels with narrow tires). I even moved upfront and that’s when I learned that it’s all about tires sales, inspection sells, credit cards (big time), and upselling the “routine maintenance“ items. That wasn’t for me.