Trainers only have an "in-house" certification
Ah, the joys of a highly unregulated industry.
If trainers at your facility hold a "certification" provided by the facility itself, with no other fully vetted and accredited certifications to their names, be very cautious about listening to their advice. Anyone can throw up a dumbbell and call themselves a trainer, and any facility can put together their own class for employees to "certify" them. This doesn't mean the information they're providing is accurate or based on scientific research.
You're told you need a side of supplements with your membership
As in protein powder, metabolic boosters, or mysterious shakes and pills the gym staff assures you are necessary to maximize your gains at the gym.