I think everyone forgot that this game was made in a new graphics engine and tons of the features that we saw in the game are totally new to the series...
I mean cockpit cam first time ever and they did a great job, weather effects also for the first time ever (cycles) and it reminded me of Race07/GTR Evolution weather effects which are almost the same...it just need a "wet" texture above the car to give it the wet look and also it needs the same water effects on track like F1 2011 too...but the rest is well made having in consideration that this is the first time for the game...
Also day/night cycles and lighting at least for me and for others is one of the best in the market not just in the genre. Even pCARS is doing a great job but the colour palette of GT5 is tons more realistic and the overall lighting system is more complex and gives to the game a realistic unique look and not over saturated like pCARS. (i have it yes).
Of course the weather system could be better if they do it as pCARS (clouds moving and changing to form storms) or one of the best in the genre but not complete (the Moon at night is not moving and the stars/sky don´t move and this is important to give the feel that the planet is actually moving, in Skyrim or Arma 2 is perfect but lighting not so much) is the one of Red Dead Redemption.
Video of RDR:
I mean this game to me until today it feels like a beta, a game that is still in development and they put all together to see how it works and then see what they can keep or remove and of course improve without (my guess) don´t spoil everything to the competition for the next game...now PD is way to quiet within the GT6 upcoming game...normal after what happens with GT5.
They are going to improve everything and also it is true that the PS3 hardware can´t handle all that if you want those effects and also have a 60FPS ratio all the time and constant.
I play on PC and you don´t know how hard is to make a PC that can handle everything at constant FPS without loosing the gorgeous looking graphics details all together with higher resolutions as 1080p that makes it look everything more detailed than 720p for example in an HD TV with native 1080p (mine).
So, the hardware was a problem but also how the game was made was too...we jumped from a PS2 game without weather cycles, day night cycles, cockpit cameras, low resolution tracks, cars, textures, low polygon count to a game that almost matched the reality.
In the other hand you have the competition (Forza) which is evolving from the same graphics engine in the almost same console year after year with some touches and improvements and then releasing games every 2 years...quite normal and not impressive compared to PD...lighting in Forza Horizon is awful if you compare it with GT5 lighting...the thing is that one game wants to look good or beautiful (pCARS too)...the other is aiming at a realistic look using proper colour palette combined with an amazing lighting system.
So again...all for sure can be improved and has to be because it all look as it was made till some point and then just saying "okay, this is enough...the PS3 can handle...move forward".
This is one of the reasons that i think we are going to see GT6 on the PS4...but who knows...the game could look better and have all effects enabled but they have to sacrifice the frame rate and don´t think they want to do it.
And going backwards is not the solution when you find the "ideal" lighting system and HD quality graphics.
Now we can sit and expect something even better but not worst...
Features is the other part that can be tons better and felt the same way as the graphics details and issues.
TL-DR i know...sorry.