You absolutely can use shimmer. I do. But I also don’t have that much of a dps loss from movement. From the sounds of it your positioning was bad to begin with, so your correct course of action is learning where you should be standing.
Also, you definitely don’t need to make your own keys to join a low key group. Yes, you might not get gear from them, but you get experience and importantly, IO, which is going to get you invited more into higher keys.