I have a friend who has a very strong opinion that the rules of threatened range and opportunity attacks D&D 5e are completely irrational, which is fine. As a DM he house-rules the stuff from 3.5e at the very least. His main problems are these:
You can move around an opponent, as though they are allowing you freedom for no apparent reason, with no real expenditure on your part. Creatures with outrageous speed can literally run around another creature freely until they get dizzy.
You can interact with objects freely while within the reach of a hostile creature. You can draw or pick up a weapon, reload your crossbow, operate a lever, etc.
You can pull out your bow or your javelin and make a ranged attack with disadvantage, against either the hostile creature or some other target.
According to my friend, you should not be able to do any of that around someone without them contesting it with an opportunity attack. Any skilled fighter shouldn't be letting anything like that slide. Sure, there are Feats that facilitate what he sees as the obvious thing, but those represent training and abilities beyond the norm and are optional at DM discretion anyways.
Have the developers ever explained why they moved away from "threatened squares" and why the above situations do not provoke opportunity attacks anymore?