I'm similar. I treat the slides as the skeleton to my talk and I use them to set the pace and go from there. Overly rehearsed talks always feel kind of boring; going off the cuff can have a disorganized awkwardness, but if the slides are decent and the speaker is good enough at explaining them I find them a lot more fun.

I do try and work hard enough on my slides to make sure that the stuff I'm talking about is paced well enough and I do prepare a light "outline" in my brain to remember keep points that I don't want to forget to bring up (that might not be directly in the slides), but most of the words I say are improvised. I don't know if the talks I've given are "good" or not but people generally laugh at my jokes and I've generally received positive feedback at Lambda Days.

I will say, one thing that really helped me become a better speaker was lecturing for two semesters at a local university. I tend to be a very fast talker and have been most of my life, and it's easy for people to not fully hear what I have said (especially if they don't know me very well and haven't adapted to my mannerisms). When I started lecturing, I learned how to force myself to slow down so that students could understand what I said I don't lose them in the dust.