First, the Royal Ballet's decline, which is very well-documented, began in the mid-1970s, when contemporary ballets began to seap into the repertory. From the time I came to ballet I've been reading "Ah! Finally things are beginning to be put right" followed by, in a few months, "Well, maybe not...."
Second, some critics I know who have the opportunity to watch Paris Opera Ballet more closely than I have been sounding alarms there for the past three years. One negative effect contemporary ballets do have is that, paradoxically, they don't develop individuals in the same way classical ballet seems to do. Several people have written (and I think they're right) that when the last of the Nureyev etoiles retires, the chinks in the Paris armor will be very visible. Also, the current director of the POB is very contemporary-oriented. They're still classical because of their school, and because there are people who believe in classical ballet on the staff. When they go, all bets are off.
Third, I'd nominate as Exhibit A the Royal Danish Ballet in the 1970s, when nearly everyone, Danish and foreign critics, noticed a decline. The director benched the two classical ballerinas, there was no male classical star, and the repertory was nearly completely very small-scale (i.e., 8 to 12 people) modern dances or theater pieces. This had an enormous effect on the quality of the way the classical repertory -- on the one or two programs a year it was performed -- was danced. Danish television broadcast two or three RDB telecasts a year throughout this period, so there is a lot of evidence. The RDB came back, briefly, when the directorship changed and classical ballets began to dominate the repertory again. It wasn't just the scheduling of those ballets, however, but the fact that the three people staging/coaching/directing them knew how to bring them back.
Finally, ABT is also an interesting study, from the opposite point of view. Robbins and DeMille were very upset in the mid-1960s when they heard Lucia Chase was going to stage "Swan Lake" and argued passionately against it, partly because they thought the company really wasn't up to it, but mostly because they knew that it meant a shift in emphasis away from contemporary and experimental works like theirs (which were ballet; "contemporary" in the sense of "made last year" not in the sense of a genre). Critics have pounded ABT since that first "Swan Lake" that, although they often have excellent principals, they're off-the-mark in presentation and classical style.
So that's the view from history



