Baby slings are not the culprit, improper fit and use are the problems a previous user mentioned. Just like any piece of baby equipment, it must be used in the proper manner. There are just as many studies showing that front carriers are bad for baby joints.
I used a Slingling when my baby was tiny, but didn't love the way it restricted movment in one of my arms. But it was super easy to put on, get the baby in, and rolled up super small in the diaper bag. Even after I moved to other carriers for regular use, this is the one I kept in the bag for quick trips into the grocery store and for a back-up. I even sprained my ankle and fell once while walking with her sleeping in it...she never even woke up.
When she got just a bit bigger, I moved to a Moby Wrap. It looks more complicated than it really is. I used this for more than a year and then she got a bit too long for a front carry to be comfortable...I never did master a back carry with the Moby. It can be a little warm in the summer, but not any more than anything else.
Then, I moved to a buckle-type Mei Tai carrier called a Calyx made by Mama by Design. I primarily used it as a backpack carrier and it has been fantastic. It worked great for airports, shopping trips, when my daughter just wanted to be held when I had chores to do. My daughter still falls within the weight limits and I keep it handy just in case.
Whatever you decide, carefully read the instructions and follow them. Get some outside help. Maybe Google "babywearers association" and see if there is a group in your area. Those women are experts and will have many types and brands to let you try on.