I agree, there's absolute truth that more doesn't mean better. However, the effects of losing cars will vary form person to person. Most might not find there to be a meaningful loss of cars, but there are plenty who will be used to playing their games with their own cars, only to be presented with a racing game without them this time. For example, my dad's car (2002 Camaro SS, not the red-silver anniversary model) is no longer in the game. I could technically just put the 35th Anniversary in black and roll with it, and I don't legitimately care THAT much, but it's still a bit disappointing.
My point about the cars wasn't necessarily that the car count bothered me. It's about the price of the DLC, which drives me insane. Skipping it is the obvious answer, and I have, but like I said, having those Achievements listed as unfinished on my game is a bit bothersome. If they just cut back the cars, I would have gotten over it almost immediately. That they put a $50 price tag on getting the game to half its predecessor's number of cars (regardless of detail, I know), it's just a crazy cost.
The real content issue that bothers me is the tracks. I know, they laser-tracked these tracks or whatever...I can't say I actually care. What I care about is how they went from 26 tracks to 14. In all honesty, Forza 4 got a bit redundant towards the end with that number of tracks. With Forza 5, basically every event in the career mode involves racing on every track, because there are so few tracks in the game.
That's admittedly tougher to put up with, because it's so much of the same thing with every event. However, the real punch to the gut there is that basically all of my favorite tracks are gone. I loved Nurburgring, as I think most did. I was also a big fan of Maple Valley and Fujimi Kaido, and they're gone (with Bathurst being the closest thing to that mountainous racing, at small sections).
Really, the car count didn't bother me, it was the Season Pass's price tag. The track count...that actually bothered me.