Heavy overhead pressing should be a part of your shoulder training, but for fully developed delts you'll also need some higher volume, longer time under tension exercises. One way to do this is with combo exercises and pyramid training.
Here are four shoulder exercises that use the pyramid loading scheme. Most of these are combo exercises, meaning two different exercises performed together. For most of these loading protocols, tap out at 6 reps because this already equates to 21 reps per exercise (or 42 if it's a combo move) because of the pyramiding rep scheme.
Grab a kettlebell that's about 20 pounds lighter than what you'd use for a single-arm overhead press for 6 reps.
Start with one kettlebell swing.
Transition right into the rack position for a press. Do one press and go back to the kettlebell swing, but now for two reps.
Complete two reps of the overhead press. Continue this pattern until you hit 6 reps of each.
Load up a barbell or a practice bar. Adjust your hands so that they're outside shoulder width.
The snatch is somewhat of a combination of a front raise and a snatch, essentially a front raise with some hip drive.
For each snatch, do a wide-grip overhead press, ramping up to 6 reps.
Pick two different weights. The overhead press weight will be heavier than the lateral raise weight by 10-15 pounds.
In one hand, take the kettlebell or dumbbell into the rack position. The other hand is at your side with the lighter weight.
Complete 1 rep of each, then ramp up by a rep until you get to 6.
You'll need a sled and some type of suspension training device for this. We're going to be pairing an overhead press with a reverse flye.
Ramp up by 1 rep for each round until you get to 6 reps.
You'll need a decent amount of space for this one, so use it when you can.