“not hat I know of, but as you may know their was a big machlokes at the time when some tried to add elements of simcha to Judaism”
First of all, unless one of those specific “elements of simcha” was applied to slichos, you have no point in bringing it into this thread. Chassidim didn’t invent nor do they have a patent on simcha.
The point is, Carlebachers and other neo-chassidim (not actual chasidim) have purposely blurred the lines on when we’re supposed to be happy and when we’re supposed to be serious. Slichos parties are just an extreme and recent example. I’m sure the general problem is something that’s culminated in people’s minds for years. If you start selling out the Torah in the name of making it more engaging, meaningful, fun (whatever word you want to use) for the young people, you will inevitably end up with Reform Judaism in the end.