Most gyms are public and there will always be someone else working out when you work out. If you sit there waiting with a frown on your face watching every slow rep the other person does or (worst) ask to jump in for a quick set, you are missing an opportunity to break an old habit. And, breaking that old habit just might help you improve you goals. Why not try a new (don’t be afraid) machine or use a different weight. The body responds to habit and change differently. The different angle, weight or pace hits the muscles with something new to deal with. It will struggle to adjust but it will recover and conquer. We are made like that. Well that’s only if we let the mind get over it. Don’t even think about it. Just do it. Don’t let the weight room turn into a wait room. You will feel so much better at the end of your workout.
It's your choice you can really use the weight room or wait in the wait room.