I am using Netcup over the course of 20 years now and tbh never had any problems. Their customer service is very friendly and they responded quickly to me every time. Sorry to hear your story, but I think this is an exception? I had domains there too, but moved away because of functionality. But my main hoster is Hetzner for a decade now. But because of vendor lock out, I am glad to have Netcup too, especially if you consider the price!