1. Roll back the ball 15%. That would mean less land required for golf. 7,000-yards would be a stern test, and a whole bunch of courses would regain some teeth. Most golfers would never know the difference if they weren't told, as they never hit the ball consistently solid.
2. Reduce the set to 9-clubs, maybe 10. You'd reintroduce shot-making and with the ball going shorter, you'd reintroduce strategy. Courses could get wider, allowing for strategic options for the better players, instead of launch and gouge and the maintenance practices that follow in trying to "challenge" these golfers. This reduction in clubs wouldn't bother the average golfer either, in fact, it would probably make the game easier by simplifying it.
With a couple easy moves, golf courses would become more interesting, challenge restored to the game, to classic courses and we'd require less land for future development.