People just don't know how to train legs. You don't build leg size with 3x5.
Here's how it goes for strength AND size.
Squats 1x5-8
Leg Press 1x8-12
Leg Extensions 1x12-16
Increasing the reps for each exercise each session until the rep threshold is reached. Then add weight and start over. 2nd and 3rd sets have only enough rest to set up the weights.
The first set can be fast and explosive, this is your strength set. Rep tempo on the second and 3rd sets is slow and squeezing, all about the burn and pump. These are your growth sets.
After training your legs STRETCH YOUR QUADS while they are still pumped. 30-60 seconds, good time to work on your front splits. It will hurt but you will notice that you can stretch farther when the muscles are fatigued. Great thing to do for your flexibility.
You're legs will grow quickly like a motherfucker. That's how to make legs grow big, strong and flexible. Don't forget your groin.
Same thing for hamstrings:
Romanian Deadlift 5-8
Glute/Ham Raise 1x8-12
Leg Curls 1x12-16
STRETCH again.
There's a simple trick for calves. Some people think their calves can't grow, this is bullshit.
With calves you have to pause at the bottom for at least 5 seconds or your achilles tendon will take all of the load, it's a reflex. After 5 seconds, the muscle takes over. Most people, even if they don't bounce, their rep tempo is too quick for growth.
Your rep tempo on calf raises is 5 seconds lowering, 5 seconds at the bottom, explode up and 5 at the top.
Calf raises 3x10, nothing special. Just do the reps right so your tendons aren't taking the load. You will notice the difference immediately and want to quit.
You won't be able to walk for a week.