This may be just based in my own hearing abilities, but I think that many will agree that the post-hiatus Fairy Tail OST is quite different from the pre-hiatus OST.
For example, a lot of the pre-hiatus music were variations of the original theme song, and there would always be some kind of reincarnation of that theme pre-hiatus no matter how far the music started to stray from the original theme song.
But the post-hiatus music seems much different, despite the music being composed by the same person pre and post-hiatus. It never brought back the old theme, and briefly revisited one of the sad songs from the pre-hiatus series.
Is there any reason for such a drastic change in music, besides of course, time? It seems as if the composer Yasuharu Takanashi is trying to stray away from the old Fairy Tail style of music altogether in the post-hiatus series, which I think is quite strange, since I think that many will attribute some of the pre-hiatus serie's success to be largely due to the music being very aptly chosen and composed very well to emotionally connect the viewer to the show.