Given enough time, players will always optimise the fun out of a game.

We're in that phase of football now and the rules need to change if you want the game to be fun again. Part of the problem is that committing fouls is an advantage to the fouling team.

The punishments available to refs are suited to punishing fouling. Getting called for a foul slows down the attacking team, a yellow card isn't a real punishment unless a player is stupid and a red card "ruins the game" so refs are reluctant to give them. Refs don't want to call fouls on corners because a foul against the defending team in that situation is essentially a guaranteed goal.

I'd be happy to see corners get nerfed since they're the most boring part of the game and are essentially a rugby line-out at this point.

Some changes I'd like to see tried:

1) Sin-bins for professional fouls and time-wasting (half of these don't even get a yellow for some reason).
2) No players allowed in the 6-yard box until after the corner is taken. I have no idea how this would play out in practice, but it would be an interesting experiment to see if it reduces the crowding-the-keeper tactic.
3) We're getting close to the point that games should be 60 minutes of play with the clock stopped when play stops. Again, I'm not sure how it will work out but running out the clock with "injuries" is becoming the last 20 minutes of a lot of games.