Honestly I think I have this covered. 99% of your average gym users, inc myself all too often, do the same damn thing and hope for shit to happen. One very easy trick a coach (more so when you swap coaches) do is get you to change shit up.
So if, for example and like me, you're a big fan of lowish volume then high volume WILL stimulate changes.
Another point is you'll see members say stuff like 'I'm training really hard' (aka 'killing it'). Most of the time they aren't. Getting a nice pump or feeling a burn while half high on a preworkout is NOT killing it. How do I know... cos they aren't making it happen.
Then there's the lack of food vs lots more PEDs thing. Don't kill it and then not eat enough to grow.
Finally, as Stevesmi has said, go big on the compounds vs pissing around with concentration curls etc. Bench big, press big, pull big and you'll be big. Rep out on some fancy curls and neglect triceps and you'll still be waiting.