How can melee attackers do damage if they can't end their turn in someone else's space?

Question

I'm a DM of a party of 3. As a new DM, I'm still learning the rules (yes, I screw up. I'm not the best DM) but the rules on space are very confusing. All 3 PCs are melee attackers - a phantom rogue, a bladesinger, and a melee war cleric. My problem is that in the PHB, it says;

You can move through a nonhostile creature's space. In contrast, you can move through a hostile creature's space only if the creature is at least two sizes larger or smaller than you. Remember that another creature's space is difficult terrain for you. Whether a creature is a friend or an enemy, you can't willingly end your move in its space. If you leave a hostile creature's reach during your move, you provoke an opportunity attack, as explained later in the chapter.

How can melee attackers work with this if they have to use their action to disengage every time they enter someone's space, or risk an opportunity attack? This seems to promote only ranged attacks and spell casters.

Answer 1

Your reach is five feet, so you don’t have to enter the target’s space to attack.

The rules for Melee Attacks state:

Most creatures have a 5-foot reach and can thus attack targets within 5 feet of them when making a melee attack.

Since your reach is (at least) five feet, you do not enter the target’s space to make a melee attack against them.