The primary issue with Ruth Graham's identification of Chandler as the problematic element with Friends is that she gives insufficient weight to his context. Chandler, in the first few seasons, is meant to be a stereotypical child of 1970s divorce: he was both quite young when his parents' marriage fell apart, and they--crucially--appear to have done nothing to keep him out of the details of their fighting. The adult Chandler is not a Nice Guy, i.e. the sort who believes that he deserves love (or at least sex) from the particular objects of his desire; he's a guy who does not believe that he deserves or could have a lasting relationship. It's for this reason that he seeks out women with imperfections or for whom the relationship is doomed from the start. Indeed, Chandler's inability to manage relationships is one of the central themes of season 5. But it's solved by the time he proposes in season 6, which means about half the show's run happens with a relatively-stable Chandler Bing.
Friends does have two serious problems on re-watch. The first is an obvious and notable decline in quality that occurs no later than season 6; on a previous blu-ray re-watch (thanks for the wedding present!), I had pegged it in season 3. There's no reason for Monica and Chandler not to get engaged at the end of season 5, but it is instead dragged out for another year, just the beginning of extending plot points for the sake of keeping the show running. The second, and more notable, failing is the manner in which Ross-and-Rachel overshadow everything else. The screen time they get as a couple is very minimal: about one year between seasons 2 and 3, one episode at the beginning of season 4, and then not again until the finale six years later. Because they are Fated To Be Together, every interaction or potential interaction gets disproportionate attention, and the whole thing falls apart. Thus the eternal question: given writers who are unable to accurately portray the interesting dramatic possibilities of a healthy marriage while needing the happy ending expressed in the possibility of a healthy, long-lasting marriage, is it better to keep a central couple apart for as long as possible, as with Ross and Rachel, or put them together quickly and never allow more than the slightest hint of friction between them, as with Jim and Pam? Or should we just admit that all tv shows, because they have runs of uncertain length, will borrow liberally from melodrama and soap operas, and go read books instead?