Well, the game has somewhat declined in quality. The game is less about what to find combos with...it's more about having answers to anything and everything. Not nearly as bad as the TeleDAD era, but still sort of up there.
I don't really have time to talk about all of these in great detail, but here are the most significant changes.
First off are Xyz Monsters. They're similar to Synchros in the sense that they're stored in the Extra Deck and require monsters of specific levels, but they're a lot more general than Synchros when it comes to requirements. The Monsters used for the Xyz Summon stick around as 'Materials', which are used to fuel the effects of the Xyz Monster. Some even give you negative effects when they're out of materials...
Most deck themes from the early 5Ds era are dead...really the only thing that's still alive and kicking from that period is Destiny HERO TeleDAD. DAD is still at 1, but Emergency Teleport and Destiny Draw are back at 3, making the deck sort of alive once more.
These decks make the meta--I'll give brief descriptions, but not huge ones.
* Dino Rabbit: These decks have an answer to everything--with one card, they can easily get out 2400 ATK Solemn Judgments and 2300 ATK Divine Wraths. They spam Xyz Monsters and control the field, and generally run a ton of traps. They aren't harmed by banishing (removing from play) at all, so they often play Macro Cosmos and/or Dimensional Fissure.
* Fire Fist: A series of Beast-Warriors that depend on the 'Fire Formation' Spell/Trap series. Fire Formations have specific effects and stick on the field for a small ATK boost after their use, but they're fuel for the effects of the Fire Fists, which in turn, if successful, can grab even more Fire Formations. They have two boss monsters: one negates the effects of every other monster, and the other recycles Fire Formations WHILE shuffling the opponent's cards into the deck.
* Mermail: A new take on WATER decks. Mermails swarm the field with huge beatsticks that tribute others to utilize powerful effects, like hand destruction and attacking twice. They're supported with the Atlantean archetype, which consist of WATER Monsters that have effects that activate if they're sent to the graveyard as a cost to activate the effect of a WATER Monster. When your boss monsters require 1-3 WATER monsters to be discarded and Salvage being able to get back your fuel, you have a very diverse deck that can come back pretty quickly.
* Dark World: With a new structure deck, Dark World decks are dumber than ever. I don't even want to talk about these, they piss me off so much.
* Agents: Again, a new structure deck brings these to the fray. Agents now have a searcher (which doubles as a Tuner) and a boss monster that destroys a card each turn assuming you have a LIGHT Fairy to banish from the graveyard. They can easily manipulate how many Fairies get into the graveyard to get out Archlord Kristya, something very difficult to permanently remove from the game.
* Prophecy: Very similar to the Fire Fists in the sense that they rely on a specific set of Spells (the "Spellbook" series), but they're completely different. They're all Spells, all the time. They search, they cycle through the deck, they give you a second draw while recycling Spellbooks, get out powerful beaters fueled by the Spellbooks, and so forth. "Divine Judgment of the Spellbooks", coming out in Japan in 10 days, is the most broken thing ever. Really.
* Exodia: While not exactly meta, it's still a popular deck with more ways than ever to stall out your foe. Cards like One Day of Peace brought Exodia back into the spotlight, letting it get into the Top 8 in Worlds last year! Pretty damn impressive, considering it's a gimmick deck.
...I spent more time typing that than I thought. Well, hope I helped sorta bgdfigdhdh
EDIT: Forgot one. There's probably another, but whatever
* Chaos Dragons: This deck starts out a bit slow, needing to mill with Card Trooper and Lightsworns before being able to do much, but once they get going, they won't stop very easily. Their boss monsters are as easy to get out as banishing a LIGHT and DARK Monster from the graveyard. The death of Lightpulsar Dragon becomes the birth of another dragon, which can then revive Lightpulsar to create a loop of powerful beatsticks. Truly an annoying deck that's still good even after they were crippled with the ban of Future Fusion and the limiting of Chaos Sorcerer and Red-Eyes Darkness Metal Dragon.