you dont need 1.5 hours in the gym unless youre doing some serious training.
ive been a member of about 7 different gyms in life, ranging in member size from tens to the hundreds. ive seen a lot of people work out and ive worked out with a lot of people. rarely do i see anyone do anything correctly. mostly i see everyone just concerned with hitting some arbitrarily specified number of reps. no one pays attention to form, the speed with which they do their exercises, and you can tell by these fundamental mistakes that a lot of people dont know how to work their bodies out efficiently.
bad form in the gym will waste your energy, insidiously damage your body, burn little fat, build/reinforce muscle very slowly, and take a very long time. youll end up wondering why you put in so much gym time for so little return. its likely not your diet and likely not that you dont work out enough.
i dont know you or how you work out. i just know what i consider to be "typical" or "average," and i feel 1.5 hours in a gym can easily be condensed into 45 mins. 30 once you have your workout committed to memory.
you cant describe good form to someone. you have to show them. ive even seen cheap/crappy personal trainers with people that give 0 tips as to their clients form - you just watch the client flinging weights witht their arms or pulling bars down with no control, just making a jerky motion and letting gravity do most of the work.
muscle isolation, slow and controlled negative motions, correct posture, and proper form will be the only effective means of a light workout. you can probably cut the number of exercises you do to a certain area in half this way. ive showed people the proper forms when lifting before, and they realized they couldnt control 60% of the weight they were doing previously. they also realized that a low number of reps started to burn them good instead of needing as many as before. this doesnt suggest low reps is good, this implies their body was simply not used to doing it properly.
so yeah, i understand not wanting to spend 1.5 hours in a gym every day. maybe find some oneinto professional athleticism that can teach you power cleans (really tough to get form down on those) or some other multi muscle movement, and you can even cut your workout down to 20 mins. ive met professional weightlifters / body builders that only work out 40 mins a day, this is entirely due to perfect form.