Well, I think "the quality of my Adventures cards was lower than for other expansions I bought." is true for 100% of people unless maybe they have only bought the reprints of some of the early sets that ran into the same issues.
The real question is whether the quality is "noticeably" lower/different, and unfortunately that is very subjective.
The "bendy-ness" is absolutely different on 100% of Adventures cards that exist today. I am sure anyone can tell the difference if they closely inspect the cards. Can you tell the difference when you are shuffling though? Maybe... depends on how you shuffle. You better not be able to tell the difference with my cards, because they are sleeved, and if you bend them, you will get on my bad list.
The coloring is another thing, but also subjective. I posted some pictures of mine somewhere around here when I got them, and you could for sure tell which cards were which by looking at the pictures, but it isn't super obvious, and I don't think it is something that will be casually noticed during a game with my cards. Some others posted pictures of light colored backs that were much more obvious (Chris is me I think).