So in all honesty, what is it that changed since the 2015 Vintage Championships? I personally consider 2014/2015 to be one of the finest metagames of recent memory.
There was such a depth of choice.
Want to play Oath- you could play normal Oath, Show Oath or Salvagers
Want to play Shops- choose from Stax, Martello, Terra Nova, or even Tiny Robots
Want to play U/R or U/W- You could play Delver, Monastery Mentor, Blood Moon, or Standstill
Want to play control- Thieves, Tinker, Control, etc
Want to play combo- Belcher, Doomsday, TPS, Dark Petition, or Dredge.
And even rogue decks like BUG, WW, Humans were very relevant.
Any one of those decks could top 16 Worlds or win a local tournament (except maybe Belcher ;)
So what happened? How did the meta change so abruptly?
I think Chalice getting restricted, might have done more harm than good. People moan about x4 Chalice shops, but some players were already starting to cut Chalices right before it got restricted. Chalice penalized the "turbo lifestyle," but also penalized shops with some dead draws, or variance cards.
The power of Monastery Mentor was too new.
The printing of Hangarback took shops players into the dormant area of Ravagers, perfecting the deck. Many players weren't even playing 8 spheres in 2015. Now instead of having some situationally dead cards (Chalice, Tangle Wire), they could be all in on the ground assault.
Lastly (late edit): I also think that during this metagame, there was a foil to each deck. The Rock-Paper-Scissor was in full effect. If you were a shop player, you were not excited about sitting down across from Oath. I think right now, Mentor and Shops are so powerful, they really don't have an enemy deck. Hence the fatigue with the format. If there is any positives to the current Meta, I would venture that "matchup luck" is at an all time low.