Sure, there are bad builders and if you're having something custom built you need to educate yourself (or hire someone trustworthy to monitor), but there are so many things much better than a 50 year old house, at least if you're in a climate that has lots of degree days.
Maybe in San Diego it doesn't matter as much.
Of course, the shittiest 50 year old houses have mostly been knocked down, so the remaining stock gets better and better ...