Both comparisions you have used actually perfectly illustrate why GT5s progression fails.
As I said before, I agree with this, up to a point.
With exception of the PSP version, I've played every Gran Turismo out there. The truth is that, although not as bad as in GT5, grinding, repeating races and having to be smart with your resources as always been a part of Gran Turismo. At the beginning, it was one of its greatest assets, actually. I don't even want to talk about things of the old games like mandatory licenses or some of the ridicously hard races, but I think it's part of what I've said before: this is not a game for everyone. I'm sure that almost anyone can pick up a NFS and have fun, even if you don't are a racing fan. But GT is a completely different experience. Still, as I've repeated a couple of times by now, GT5 is not exactly well-balanced.
In the case of the RPG system, I think that you are going too easy on it. I remeber when I bought FFX. As a new( back in those days) generation RPG I was hoping it to be more user-friendly and grinding-free. You can get to the third quarter of that game by just going straight in every dungeon but, by doing this, you'll get your ass awfully kicked after a certain point. So it's pretty simple, in many RPG's, specially japanese ones, grinding (in the boring, repeating, and sometimes rewarding, kind of way) is part of the gameplay. Why people still loves them?, because there are some who like that and, more importantly, learn to make it interesting for themselves. I repeat, I don't hope for everybody to like it, though.
I think that one of the biggest "problems" with GT5 is the fact that we, as consumers, have changed our tastes in gaming in recent years. I remember when we had "Single-player mode" and no "campaing", right before the appearing of things like COD4 or Halo. What I'm saying is that GT is not Shift, Forza or Motorstorm (And I love many of those games). After a week of playing GT1 I knew why I loved it and, maybe against what most of the posts around here seem to be about, I'm very glad that GT hasn't tried to change it just to compete with those, totally different (in style and gameplay), kind of games.
In my previous file I got up to 250 cars, level 33 in A-spec, level 14 in B spec, all licenses (very few of those in gold

) and 5 special events. I really wanted the ferrari F1 but I wasn't trying too hard. I started to having fun, competitive and hard races on-line. After a couple of hours in there I'd grind in some races but not with my FGT, but with more low-powered, tunned and customized cars; trying new racing styles, settings and stuff like that. After that I'd get into the seasonal events with (when the events were about one model only) a slightly tunned and not overpowered car. In a couple of weeks I had like 9M credits and I never got bored.
Finally, I don't want to get out of line in here but, to be honest, I think that many players don't like hard races and don't know a thing about sport driving which, in a driving simulator, is a very important thing.