Rugby is great when it's a level playing field.....
No matter what the sport, a good competition is one in which everyone has a chance of winning, even teams at the bottom of the ladder are competitive and everyone abides by the rules agreed to by all.
Beyond the scholarship issue one of the underlying issues to the GPS comp is that there has been what you would describe as 'structural change' at some schools and a more liberal philosophy regarding education and sports choices.
It wasn't that long ago that tennis (1972), basketball (1975) and soccer (1988) were introduced to AAGPS. Prior to this your only winter sport choice was pretty much rugby, basically compulsory unless ruled out due to medical reason.
Some schools have embraced the other winter sports more than others. Not sure which schools it is still compulsory at or where they cap the other winter sports teams and where you are not selected you end up in rugby, so if anyone knows...
So some schools stick to the traditional rugby, rowing and cricket more that others.
Some exclude you joining their school based on unacceptable academic capability. ( I prefer this terminology to 'selective school'.) Underlying this is the fact that it is on average easier to turn a good sportsman into a reasonable scholar. However it is a lot harder to turn a scholar into a reasonable athlete. This makes even competition hard.
Some schools take a more liberal and some would say a more modern approach to the sports they offer. This impacts their depth in rugby.
Some have also become more multicultural that others. Rugby, cricket, rowing is not necessarily strong in these cultures.
It comes down to personal choice, and I am not commenting on one school being better than the other.
My point is that 50 years ago the GPS schools shared a more similar approach to education than they do today. This makes the principle that a good competition is one where everyone has a reasonable chance to win hard to achieve and may see the GPS competition slowly erode even without the impact of scholarships.