My machine isn't thread-picky either. It's a 2 year old Janome 6600, so fully computerized, "modern" machine. I have yet to find thread it doesn't like. Ditto for my travel machine, Janome 3160QDC; another modern computerized machine.
I don't like C&C just because I think it's way overpriced. Connecting Threads cotton spools are (IMO) roughly equivalent quality, a single spool is priced almost the same as a spool of C&C at Joann's but it has much, much, much more thread on the spool. I did the math at one point and according to my figures, a spool of C&C costs about the same per yard as Aurifil! Plus there's so little on the spool, it runs out too fast for my taste.
I still have a few dozen spools of C&C I'm slowly using up, no problems with any of it. I just don't really like it.