I mean I've never heard of anyone screwing up adding refrigerants to their AC system, and I've known plenty of people that have done it. It's really simple and you'd have to catastrophically screw something up to put yourself in any real danger by doing so. Also the pressure is about the same as inflating a tire in the low pressure valve where you're adding the refrigerant. It seems like you'd only run into danger if you were mixing refrigerants or completely evacuating your system, which you'd want a professional to do, as the recharge kits aren't meant for a replacement of an AC inspection.
As far as I see it the recharge kits are used as a troubleshooting tool and temporary fix, not a service replacement.
The only things that seem like it could possibly make worse is if you didn't know what you already had in your system and you mixed two things or if you used a refrigerant with sealant that could cause issues with other components like your compressor, hoses or pumps. Overfilling to the point of causing permanent issues is pretty hard to do and you'd have to be purposely negligent.