I can only assume you are right.
I have to say, I am very disapointed in the game. Whilst its potential is no doubt incredible, I am not in the position to spend a heap upgrading hardware for the game. The playability of 2004 with addons far out performs FSX on my "average" setup.
What do I prefer on FSX ?
The water, the road and airport traffic, the default scenery, the adventures
What don't I like on FSX
FRAME RATES, blurries big time on both scenery and aircraft, the aircraft sounds don't seem as good, lack of AI traffic even at 100% which hammers framerates even more !
What do I prefer on FS2004 ?
The framerates, the addons without affecting framerates, overall playability due to performance requirements.
To fly around Fly Tampa's St Maarten scenery on FS2004 is incredible. Moving boats, cars and an incredibly realistic scenery with amazing framerates is a shear pleasure.
Obviously that is just my opinion and I am sure there are many who disagree. Good frame rates is crucial to my sim experience as is a lack of bluries.
anyway, thanks for the comment.
Neil
For the blurriness of the aircraft, it's only linked to the settings in the game (global texture resolution if I'm not mistaken) and eventually to the settings of your video drivers.
When it comes to the blurries of the ground, I have a very old CPU just like you, and the only thing that really helped reducing them is the SP2 for FSX. You should give it a try but keep it mind that it will introduce some visual problems with FS9 aircraft addons.
For the AI traffic, of course the default one is reduced. It's completely fake anyway, so who cares ?

For that precise case, the famous freeware addon "World of AI" is your friend, it will add a LOT of REAL AI traffic, but you must have heard about it already.
For the fact that FSX is not performing very well on old computers like yours and mine (I have a PIV 3,2 Ghz, 1 Gb of RAM and an unstable -too old and overheating- 6800 GT), even though SP2 has helped a lot, there's not miracle to expect, FS9 is still the best balance for visual quality... unfortunately, I got addicted to the FSX new functionnalities, so I cannot switch bak to FS9 anymore.