Hmm, what's changed since Shadowmoor? That was I think 2 blocks before I started (In Zendikar).
Yeah, let's start with blocks:
- Shards of Alara- Actually 5 demi planes, each focused on a different three colour combination.
- Zendikar - D&D adventure world. Land matters theme. Considered one of the best sets of this decade. Turns out Cthulhu was sealed here. Most Cthulu-y cards are colorless and have a transparent background over full art.
- Scars of Mirrodin - The first block to revisit a plane. Phyrexians grow from Phyrexian microbes that contaminated the plane and take over. It is sad but awesome.
- Innistrad - Gothic horror world. Graveyard and tribal themes. Two sided cards that transform from one side to the other show up. Considered by many to be the bes block since Ravnica.
- Return To Ravnica - Speak of the devil! Ravnica's still Ravnica. It's still cool. Actually, nothing's changed at all. Still hasn't.
- Theros - Greek myth world. Enchantment creatures get a set.
- Tarkir - Wartorn Mongolia experiences time travel plot, becomes dragon-ravaged Mongolia. 3 colour theme, but in combinations we didn't see in Alara. So many dragons.
- Battle For Zendikar - Here we switch to sets of 2 blocks instead of 3. That's supposed to be the new normal now.
Back to Zendiakr to fight Cthulus. They kill two in antidclimactic fashion, but the ultimate Cthulhu escapes to... - Shadow Over Innistrad - Gothic horror goes cosmic horror. They did the segue pretty nicely actually.
- Kaladesh - Steampunk India. Artifact theme and energy counters as a resource. Pretty cool, but the story ain't so great.
The big gameplay changes:
- Mana burn is gone.
- Combat damage is off the stack. It was still on the stack for Lorwynn, right?
- Lots of wording changes. Removed from the game is no "exiled". Comes into play became "enters the battlefield". Tokens are "created". Cards with multiple options list them as bullet points like in this list.
- Creatures have gotten more powerful and noncreature spells less powerful since Lorwynn.
Formats:
Legacy and vintage costs thousands of dollars to get into, and the format is dying from lack of new blood and official support. As the audience grows, those old cards have gotten more and more expensive.
Extended was killed off after WOTC realized that Mirrodin rotating out would wreck the format. They created modern, which is everything from 8th edition forward (thereby keeping Mirrodin from ever rotating).
OP stuff:
The biggest thing to break standard was probably
Jace, The Mind Sculptor. It wasn't Mirrodin or Urza levels of crazy, but it was pretty crazy.
Stoneforge Mystic also got the boot I believe.
The offending deck was called Caw Blade and won by strapping powerful equipment onto
Squadron Hawks since you always had 4 copies for backup to get the equipment damage through.
They also printed some cards that caused problems in older formats. Mostly those came from New Phyrexia and Khans of Tarkir.
Other stuff:
WOTC's started releasing products that aren't standard playable. Multiplayer-focused decks, and sets of cards drawn from modern and legacy.
They've also introduced a new rarity- "Mythic rare". Mythics replace the rare in 1 out of every 8 packs and are expensive to buy as singles.
There's a basic land in each pack now. Return to Ravnica put dual lands in that slot though.
Prereleases got a couple of revamps. Most notably, you can now play your prerelease card at the prerelease. They did choose your colour/faction prerelease kits for a while, but had trouble balancing them against each other. Prereleases are just generally a bigger deal now.
The EndI was around at the forum death. WOTC really shot themselves in the foot with that one. Years of worsening management took there toll, and then came the "white death". Maybe Barinellos has some pics of the last software overhaul they did. One of the Expanded Multiverse fanficers (that's a thing now. Check out heir work; it's good) even wrote a story not so subtly about it. The forum's population nosedived and within a few months WOTC "Decided to concentrate their resources elsewhere".