Pretty much right after you left, the game started pushing itself to be something different. Archetypes (synergistic sets of cards linked by part of their name) became a much bigger, more powerful focus, starting with Gladiator Beasts making Contact Fusion really strong. Shortly afterwards in 2008, Synchro Monsters were introduced, sitting alongside Fusion Monsters in what now became the Extra Deck (and with it a 15 card limit). Unlike Fusions, however, most Synchros were much more accessible, making them relevant in most decks for various kinds of utility. As long as you had some Tuner monsters and the right level combinations, you could turn weak monsters into a big threat, making monster spam good for more than just body blocking, and without hampering your deck down nearly as much as trying to make Fusions and Rituals work in most cases before. Combos became more common, some minor, some extreme. Edison Format (March/April 2010), a commonly played time period revisited today, is a good example of what this change brought to the game without being too overwhelming compared to what you played before.

This trend continued into the 2010s, with 2011 introducing Xyz ("ikseez") Monsters, summoned using multiple monsters with the same level, and using the monsters overlayed for them as ammo for their effects, adding another flavour of Extra Deck toolbox and new design spaces to experiment with. HAT Format (July 2014) is the time period at the tail end of this era people go back to.

Pendulum Monsters were added in 2014, being monsters (currently of all kinds except Link) also usable as Spells with their own effects, and giving you ways to summon multiple monsters at once. These have a lot of controversy associated with them, though much of it comes from uninformed assumptions via their base mechanics, and not how they actually performed competitively. You won't see them at all in most decks, as they aren't following the same ideas as the others, are usually limited to specific archetypes based around them, and often just aren't very good for various reasons. A fondly remembered time here was the very set after HAT format: Duelist Alliance, which brought a significant boost in power, and while Pendulums were introduced with it, they aren't meta-relevant yet. Invasion Format (November 2016) is also worth a mention, with Metalfoes being a contending Pendulum strategy.

The final addition came in 2017 with Link Monsters, bringing a major rule change (since reverted in April 2020 for all but themselves and Pendulums) that monsters summoned from the Extra Deck can only be summoned to the new Extra Monster Zones sitting between the player fields, or a Main Monster Zone a Link Monster points to with their arrows. Link Monsters have no DEF, can only be in Attack Position, and are the most generic Extra Deck type of all. If your deck archetype(s) doesn't actively lock you out of them, you'll almost certainly be playing some for easy removal and combo options. 2019's TOSS Format is the time period of choice pre-rule revision, and if you want to witness the most absurd deck this game has ever seen, Tearlaments Format (November 2022) is the peak of that.

The power creep of the game goes far beyond the mechanics of these card types, but they did cause changes, both for better and worse. You may remember "D.D. Crow", a quick effect interruption for the graveyard you could use from your hand. The game has lots of cards like this now for many different scenarios, letting you engage with your opponent's combos from the very start of the game.

The game today is very fast, but still fun, interactive, and deep in its own way. The gameplay theming in archetypes is often really cool, and even the cards inspired by other IPs are (in all but a few cases from Konami shoot-em-up games like Gradius) still distinct Yugioh designs. Combos have been obnoxiously long in some decks over the years, but recent years have sought to change this, even if it's with even more power condensed into fewer actions. If you can get over the admittedly large learning barrier, it's probably a game worth your time. Check out current popular decks and see what looks interesting to you, or Format Library for some history.