I don't see range finders having a big effect on design. So much effects the distance we hit the ball: elevation changes (real and perceived), the lie, wind, the temperature, our physical condition, our mental condition, our ball striking ability that day etc etc. And then there's the design elements -- make sure you carry the front bunker, or watch out for that drop off over the back, need to cut it into that front flag etc.
I used a range finder for a year or two but haven't for the past 12 months. Knowing the exact distance to the pin (and perhaps more importantly other hazards, the back of the green etc) is good, but even when I knew it was 137 yards to the flag I didn't always hit a 9 iron. And sometimes I would hit an 8 iron into the back bunker because it looked uphill, or because I wanted to make sure I got on to the back tier, or because I misjudged the wind, or the lie.
It's a hard game. The rangefinder doesn't make it much easier. It made no real difference to my scores during the period I used it; although if used properly it should make you play faster.
There's still plenty of opportunity for the architect, Mother Nature and the Golf Gods to screw with us