The point is you get much more powerful hardware and cannot spring on from what you achieved before and do better with framerate?
I don't buy it, not from PD. They're suppose to be the technical wizards, not lose ground to other devs.
The longer PD don't take Forza seriously the longer it will get panned by critics and slowly lose a bit of marketshare
Compared to GT5/6 - It's a much better looking, sounding game with more advanced physics, higher detailed cars, a lot of which are on track at the same time, probably built almost from the ground up. Not just a matter of taking an existing engine and polishing it up.
As for missing features between generations, (dynamic weather/time of day) - happens all the time, with many, many game series. GTA4 was not as deep and rounded a game as GTA: San Andreas, but it was an important generational leap.
Also comparisons to 30fps targeting games is silly. Forza Horizon and Driveclub would absolutely not look as good as they do had they targeted 60fps. Look at Driveclubs VR mode, everyone said it was disappointing graphically in comparison to the core game. Forza Horizon at 60fps looks like regular Forza, which we can debate on, but I'm not looking at this GTSport beta footage and thinking it's lacking compared to Forza.
Game series' need to evolve to survive, and as I've said before, I think GT Sport refining the series as primarily online/competitive hub is the right move at this point of time. They have to nail social/connectivity/customisation (personalisation e.g. decals), along simple to setup competitive online races.
GT5/6 might have had a lot of online options, but it was for me, primarily an absolute mess and pain in the ass to get a simple race going that didn't devolve into dicking about on the nurburgring for 30 minutes to an hour without achieving anything. Pairing this mess down into a good online racing system is paramount. If they nail this, average race times to achieve a result will be way shorter, and dynamic conditions will come into play a lot less. So it makes sense to sacrifice it and concentrate on other things, and it could even allow them to make a better looking game if it's baked in.