Meh, it's an inevitability that talking about SEED will give rise to comparing it to 00. While Gundam has had some mishaps in the past (like ZZ's first half), this is probably the first time where there is a great disparity of quality between two Gundam series next to each other. I mean yes, the mileage you get with certain Gundam series varies, but it can be stated that each series may stand on its own merits, let alone be shown to be 'not too bad', like say... G and Wing, given how close they were together when aired.
Destiny was the first time that a Gundam series failed on an objective level when it came to actual quality. It cannot stand on its own merits because for hte majority part, there are few. It is the first instance of an unsatisfactory Gundam series given to us where everything that seemed so right turned into something so wrong, and every return to it through SEs and what have you have left an indelibly bad taste in your mouth.
Then when an objectively superior product comes along (00), and as people were coming along and watching it through, it was bound to attract comparisons to Destiny. And why not? The show is GOOD. The character development is GOOD. The story is GOOD. The concept is GOOD. Sure there are flaws, but there is a dedication to the product that Destiny never had. It's essentially the observation of two passenger trains, one of Destiny and one of 00. While the Destiny one started out strong and eventually sputtered and broke down at the end, the 00 one was like a bullet train that slowly gained momentum, picked up speed, and for the majority part, came to its end like a champion. When you see that, then see the previous one, are you just going to ignore the discrepancies between quailty and not say anything, or will you? I bet on the latter.
And that's essentially what is bound to happen no matter what people do. Nobody compares 00 to the original UC Gundams, nor G, nor Wing (and if they do its merely on the aesthetics and concept on the first few episodes), nor X, nor even Turn A. Hell I don't even think a "Has SEED aged well?" thread would have existed had it not been for 00. It always comes back to the previous series. It's not bad, it's not even good, it's just bound to happen whether we like it or not.