With less loft, you need speed to generate spin and launch. Sounds like you either need a softer / lighter shaft, or something with a lower center of gravity, like a hybrid or fairway wood.

Check with your teaching pro. He can assess if it's the club or your technique.

Most amateurs can't produce enough speed to gain the four iron benefits. You may need a different shaft or move to a Hybrid, Fairway.

Were you professionally fit? Might want to check out KBS or Graphite Designs graphite driving iron shafts!

As Todd said above, consider your shaft. And, As play18 suggests, consider seeing a teaching pro to tweak some things. EIther could be the culprit.

I play a GD Tour AD-UT 85S in my U500 4i and it launches plenty high enough. And, I am not a high swing speed player. I'm in my mid-sixties. From tee or turf, I have no issues getting the ball in the air. Distance-wise, I count on about 10+ yards more with the U500 4i than I expect with my T200 5i (w/Aerotech Steelfiber i95 shaft).

That said, a few years back, my swing was not as good as it is today. I could not hit a 4i back then, yet was somewhat okay with my 5i. Today, after some tweaks and suggestions from some seasoned instructors and scratch (or better) playing buddies, my swing is much more efficient. I have confidence now in both my 5 and 4 irons and sometimes think about a 3 iron (but then I have to remind myself, I'm not 25 anymore!).

Every player and every swing is different. Get an assessment from an instructor you trust. It could be in your swing or might be something fixable with a shaft change. Or a combo of both.

Give it a chance. I've had the same issue with every new set. I think subconsciously I was over swinging and not letting the club do its thing.

I have not had any issue with launching my T200 4 iron high.

During a fitting this is the "break point" if we see the ball speed of the 4 iron the same as the 5 iron its time for a 4 hybrid to gain back the ball speed and it makes for an easier launch. Very common, the break point can be at different spots for different players, but based on what you are seeing it's time to drop the 4 iron and consider a 4 driving iron u505 or 4 hybrid or even a 7 wood.