I dont think consistent mileage earning policies was a core benefit of the alliance, rather the alliance benefit is that all members are partners of each other allowing earning and burning without the need for lots of bilateral arrangements. As stated by others, having some variation in earn and burn rates is an advantage to savvy consumers who can pick the program that best suits them.

Lower mileage on discount fares is nothing to do with an alliance IMHO. Rather it is the respective airlines responses to competitive pressure. At least there is a choice - cheap fare with little or no miles (but at least get status benefits), cheap fare with the competition (no status benefits and maybe no useful miles), or more expensive fare with full miles.

I like competition on some routes. It is good to not be limited to one airline, for example trans-atlantic I can take NZ instead of UA.

Similarly with ground services. Using LAX as your example, I'd be mightily annoyed if the only *A lounge was UA's RCC, which isnt even in the same terminals that the other *A airlines use.

An alliance is not about getting full coverage of every routing possible. Until SA joins, for example there is limited African presence. There is no airline flying directly between South America and Australia/NZ. No intra-Australia flights (except SYD-MEL). Etc. But other alliances also have gaps. One World has limited routes within South-east Asia. Sky Team has no routes within Australia/NZ and limited routes to Australia/NZ. Etc.

Why would you cut out airlines from *A? No airline is perfect - they all have pluses and minuses. I'm far from impressed with my experiences with UA and AC for instance, but I'm still glad they're in *A for their north american networks.

The OP comes across as wishing *A would become one seamless integrated airline with the best bits of all its members retained and losing the worse bits. That just isnt going to happen - not only are there major ownership issues but many competition authorities would be against it.

I'm with snoopy in that the value you (as pax) get from an alliance depends on your circumstances and flying patterns. Naturally some (global uber flyers) benefit much more than others (infrequent domestic flyers).