Totally agree with you on mass participation events and inexperienced cyclists. I've had a few near misses myself over the years. I also think that closed roads tend to make cyclists less risk averse and speeds tend to be higher which I guess may contribute in part to any accidents or at least their outcome. I hit 45mph + on some of the descents in Velothon Wales and dread to think what would have happened if I'd hit the deck at that speed.
I did the Birmingham Velo last time and enjoyed it immensely, Bewdley and the Clent Hills being a highlight. Just couldn't get inspired by the route this time and with a hefty price to enter, I chose some more low key sportive for this year.
The Fred Whitton is on my list to do one year but often clashes with fell races (and I'm not sure I'd manage Hardknott anyway!)