With the announcement of eliminating tier sets, it feels like Blizzard wants to kill off raiding. I know what you are thinking, another player screaming "the sky is falling". But, with BfA and other changes from Legion, it seems Blizzard is steering the game to a more casual, open world sandbox and away from a structured game style, which is what raiding is.
Loot and gear is raining down all over the game. You can even obtain better gear from non raiding content as compared to raid drops. I am a heroic raider but my character probably about 50% non raid gear equipped. These pieces are from my mythic weekly caches, bonus week caches, emissary quests and relinquished gear from the Argus vendor. Heck, if you get lucky enough you can even top mythic level gear from some sources. Really, the only gear that is obtainable only from raiding is tier gear.
Ion said they are not getting rid of titanforging and other mechanics to increase item level from drops. This mechanic plus all the new sources for gear that is equal to or better than raid gear and eliminating tier sets, tells you where they want to take this game.
Raiding is about testing yourself against some of the toughest content in the game. Raiding is what brings people back week after week in order to progress and finally kill the end boss. But loot and gear was the carrot on the stick. It kept you coming back. And the satisfaction of finally downing that boss your team has struggled with is the reason we raid. But getting that epic tier piece, weapon, trinket, etc was the icing on the cake. Tier sets are unique to raiding. If you look at a player and see they are item level 930 but have no tier you can tell they dont raid. But if you look at a player with item level 930 and you see heroic or even mythic tier gear, you know they have beaten some of the hardest content in the game.