I don't know where you've been looking at Mexican P's that are so bad? I've had 2 both bought blind second hand, a 2003 & a 2008 that were both superb, not just for me but the guys I sold them on to were also well impressed. As long as the build quality is good - there's a whole lot of improvement in playability that comes from a proper set up. That applies equally to a £2000 bass though, not a criticism of Fender Mexican Japanese or USA.
IMO you just won't find a new bass in a shop that is set up to how it's right for you, unless you're exceedingly lucky, it's very personal & once you bond with a instrument - then you can start 'getting it right' I know I have the time, inclination, experience & patience that some may not, but I'm constantly tweaking my basses until I'm happy that it's set up as well as it can be - FOR ME! If I sell a bass I always offer to set it up for the buyer, especially if they don't like the strings that I do, then I'll change strings (at their cost & choice) & set it up. If I was dealing with a shop I would hope for the same service!!!
Cheerz, John