Ive been lifting for 20 years. Been training clients for 15 years. Have 50,000 people use my programs (yes, really).
I can tell you what “good exercises” for muscle gain in a few sentences
1. They are easy to do, and easy to learn
A bench press is easy to learn. Lay down on the bench. Keep your feet planted. Press the bar.
You can get into the finer details (chest up, elbows lined up) of course. There are entire seminars and tutorials and books dedicated to this. Technique matters.
But lets not fool ourselves and pretend bench pressing has a challenging learning curve. It does not.
You can fix someone with “bad technique” with a few minutes of coaching.
This goes for most free weight and conventional barbell movements. It does not take 50 hours to learn how to squat. Or shoulder press. Or leg press. Etc.
2. The movement aligns with the muscle biomechanics
Some call this neuromechanical matching. Others biomechanics. Or lines of movement. Or its all these things.
Call it what you like. Good exercises train a muscle (mostly) through its full range of motion, in a position where the muscle fiber is best able to contract and lengthen. Bicep cursl train biceps. A chest press trains the chest.
Find the particular version that works best for you.
3. You can add weight
If you cannot add weight, it wont build much muscle. Maybe the exercise isnt stable enough, maybe the positioning is bad, maybe its an isolation movement like a lateral raise and they are physical limitations because of the lever arm and trying to keep the body balanced.
The best movements you can hypothetically add weight for forever.
Dumb movements that are a waste of time, you cannot. They max out quickly.