D&D 5E What would happen if we got rid of opportunity attacks

[The Human Target]

The wizards (on both sides) will love it, as no front-liner in his-her right mind will want to burst through the line to get at the squishies.

I suspect in-combat movement in general will be close to nonexistent under this variant.

Tanks could use a lot more stickiness in 5e, so that doesn't bother me.