Long irons are quickly becoming like elephants, nearly extinct. There are still great players keeping long irons in their bags, and with good results. Mainly they are used off the tee on holes where driver is an uncomfortable option. The U.S. Senior Open champ this year (Brad Bryant) used a 1 iron off the tee many times throughout the tournament (and on the 72nd hole, with the tournament on the line). Tiger carries the 2 iron and uses it often with great success. You too can benefit from carrying long irons in your bag.
The only 'trick' to hitting long irons it to make solid contact consistently. The sweet spot on long irons is slightly smaller than what you'll find on short irons, and mis-hits are magnified. When you can strike the sweet spot consistently on any club, you are going to benefit from carrying at least one long iron.
O.K., that having been said, how does one hit the sweet spot consistently? Good question? A solid base is paramount. Long irons require high swing speeds to obtain good results, and a solid foundation gives the golfer the ability to swing powerfully. Visualize Ernie Els, or Tiger Woods, and the stability they maintain with their stance and posture. This is the stability needed to execute long iron shots. Be athletic, be aggresive, and hit it pure. If you do not have the ability to do this, then by all means, put a hybrid in your bag instead.
I once had a fun practice session where I hit alternating shots with a 3 iron and a sand wedge. I've never hit 3 irons more pure! The lesson that I learned there was to swing a 3 iron with the same confident ease as I swung my sand wedge. Mentally, I was swinging a club that I was very comfortable with. My recommendation to you is to try this practice session technique, alternate swings with a long iron and a wedge. You will see improvements.
As usual, it's 90% mental and the other half physical. If one would practice the drill described above, one would improve the mental capabilities and see positive physical results in hitting long irons. Good luck.