Nothing wrong with Legion its a good expansion pack, WoW is just an old game now and while the new expansions bring new content, the bottom line is its always the same stuff just in a different form such as world quests, just another way of doing dailys. The Artifact System, just something else to farm and another reason to keep doing the same type of content we've always had anyway, quests/dungeons etc... The new dungeons and raids, look different but ultimately just the same as all the others.... None of this is a problem, its just what WoW is and the type of game it is.
WoW is 10 years old, if you've been playing since the start like me and you dont find it boring then you probably arent normal.... Personally, I only renew every other month just to get my fix, do a few bits and bobs.... but then I play other games. I dont commit to raiding nothing anymore, I am strictly just a casual. I dont even care that I dont do all the emissarys every single day, simply put I only do what I enjoy because its just a game and thats that.
Play if you want too and only when you want too. If you are moaning about a game being boring then you seriously need to analyse your life priorities, its just a game.. No ones forcing you to play it and theres a million other games out there to play, so put WoW down for at least a while and go have fun in other games.
Maybe after a few weeks you will feel fresh headed to revisit WoW and then play again for abit until you are bored, then just do the same. Its what I do.
Or just dont play it at all. It really doesnt matter