I use all of my wedges and my 7 through 9 iron for chipping depending on how far I want to carry it on the green, the lie, the elevation change from ball to green, etc., Just using a 7-iron is no better than just using one wedge for chipping in my opinion. However, a 7-iron gets you much less versatility than say a 9-iron or pitching wedge. You can always deloft the wedges to get more roll. Are you actually shanking the shots or blading the ball? You must hit down on the ball when chipping especially when using a wedge. The problem with wedges is when one tries to sweep the ball rather than hit down behind the ball. The 7-iron is ideal for flat, long chips but would be hard to control for shorter chips where you have to chip up to the green.

However, all that being said, if you have improved your chipping by just using a 7-iron that is at least something. You are able to contact the ball with club face more easily without a steep downswing. Stick with that if it makes your round more enjoyable until you can get some practice with the other clubs.