I tried this once with a few new players for a one-shot, and we removed AoO for simplicity. The more experienced players at the table enjoyed examining the consequences.
Everyone runs in, attacks, runs away. Both enemies and party members use the cover and we found that the arrangement of the units on the map was much more chaotic.
Speed is more valuable
If the mobility is increased, the speed improves accordingly. Both the tabaxi and the monk appreciated jumping straight into the backlines and concentrating on the mushy ranged goblins that bothered them.
Front liners cannot do front lines
One of the reasons why a barbarian or fighter stands in front of the group and prevents multiple enemies from approaching the wizards and wizards in the background is their threatening presence and the risk of retaliation. Without AoO, enemies could easily run around and jump into the backlines, and the party's melee frontliners did exactly the same.
Being on range is more difficult, but at the same time it may be unnecessary
In closed areas where you can't shoot your bow from 150 feet away, enemies can quickly jump at ranged attackers and new tactics are required. If the character is within range because it deals more damage, it can only attack and attack 5 feet from each enemy. If they are within range because they are very muddy, they require new tactics to keep their distance.
Katz & # 39; and mouse
While it has not happened to us, a cat and mouse game can arise in open areas. Goblin races to Wizard. Magician races away. Gobling strokes to the magician. To repeat. Since there are no consequences for running away, kiting enemies in wide spaces is easier (they do no harm for running).
Overall, it was a fun experience for the players, but we decided it didn't work for us. The players enjoyed the fact that their front liners were originally there to prevent enemies from running through them. They didn't enjoy it when enemies ran away and kitesurfed. But the right thing for everyone.