There are plenty of “bad” trainers out there in any field.
And by bad it doesn’t mean they don’t know what they should be doing but rather cave into the demands of their clients that want quick results and to feel the pump.
Just look at how many people go straight into weight lifting with compound exercises without first spending months working on stability, flexibility and burst speed/power.
Then what happens is that they get into a worse state and hit a wall even if they now can bench press 1.5 their body weight.
You would be much better off benching only 100 lbs while being able to stand straight against a wall while keeping your lower back, shoulder blades, elbows and the back of your palm against the wall comfortably throughout a shoulder press.
I’ve literally seen people getting so stiff after “training” for 6 months that I’m not sure if even 2 years of corrective exercises could bring them back to their starting point yet alone to the point where they can start building muscles safely.
And while in the mid 20’s to mid 30’s they might not notice it once they hit their 40’s and couldn’t stand straight because their lats and delts were developed incorrectly and they have no core they sure will.