I've been to California once on my own (in 2017) and going again this November. The main reason why I think it's off the radar is that Disney UK doesn't push it. It's only Florida and Paris that they give you on the UK site. You have to specifically go loking for California, and they do not provide flight and accommodation packages for the UK so you have to do it all yourself. But to be honest, the California site is more of a locals park - they don't really need to advertise for it internationally. I'd been to Florida several times and really wanted to visit California but honestly I didn't know how to go about it as an inexperienced solo traveller. I have to say it was quite scary putting it all together for the first time! There is indeed also an awareness problem due to Florida and Paris being pushed so much in the UK - I was talking to soem people in work abpout my upcoming tips and there were a couple of people who didn't actually realise that there was a California site and that it was the original from 1955. They thought Disney was Florida. BTW I prefer California Disneyland and Paris Disneyland over Magic Kingdom!