Mesomorphs are the only type of man who can build muscle and look asthetic. These are the men who were genetically assigned to hunt. Shorter and more compact for more efficient fighting. Warriors. Fighters. Soldiers. These kind of men build muscle by simply stepping foot into the gym. You don't need to eat excess protein as your body is efficient at building muscle from even minimum protein sources. Unfortunately the mesomorph is also a brainlet. He is the dumb but buff stereotype
Ectomorphs cannot build muscle at all without excessive effort. These are the tall lanky aristocrats of society. They were designed for thinking. Strategy. Cunning. Wit. While the mesomorph fought. The ectomorph views the battlefield and looks for the enemy armies weak spots. The ectomorph does not need muscle as he is usually safe and sheltered from all physical activity in return for his advanced brainpower.
The endomorph is the caregiver. These are soft emotional and hardworking men suited to helping women around the house. Made for household chores, farming, industry trades, wood working and hospitality. The endomorph has a muscle frame underneath his fat, so he is capable of performing moderate strength feats. His body can only develop so much muscle before it starts to convert excess muscle into fat. The endomorph can be strong, stronger than a mesomorph at functional lifting. But he can never be strong and lean.
So do not feel bad that you're not gaining muscle as quickly as a mesomorph does. It's likely that you have a different body shape that is genetically assigned for another role in society.