Pre-patch, the meta was growing a bit stale and settling upon Crossbows play, or Knights play. (Or sometimes: Crossbows + Knights). An odd greedy defender might go Mangonel (aka: Anti XBow) + Monks (aka: anti-knights), but the game pretty much revolved around Archers (for civs like Britons) or Knights (for civs like Franks), and their closely related counter-units.

EDIT: case in point. Vikings, a civilization with numerous infantry buffs, was played as an Archer civ in practice because even with all their infantry buffs, XBow / Arbalest was considered stronger.

The biggest change this patch is a new tech for +1 pierce armor to the Longswords line, which can be researched in Castle Age. Furthermore, the entire line of infantry can upgrade faster, and cheaper. Finally, most infantry civs (Malians, Goths, etc. etc.) have gotten significant economy buffs to make them even stronger. Whether or not its enough for infantry to shine is to be seen.

There has been drastic meta changes before too but over the years the units that have been made has remained the same. The earlier meta mostly used to be around archers or cavalry , infantry was simply not viable except with certain civilization(goths) and that too only once you had the whole economy set up to spam their cheap infantry continuosly.

Theve been trying to push infantry with small buffs , and this is patch has seen some more buffs to infantry and infantry civs.

In addition to the infantry gradual bufs, full-walling in Feudal using a mix of palisades and houses became ubiquitous. Pallisades, buildings-as-walls etc were gradually nerfed. Still popular, but now there's a higher associated cost. I wonder if they're done with those nerfs, or if there's another coming. (Since this technique is still very strong... Or maybe it's that scout rushes are strong!)

More buffs to infantry. Players got better and infantry was barely used.

Several infantry civs like inka, sicilians, slavs, vikings, celts and dravidians got many huge buffs. Main change to like 50% of the civs is called gambesons, which adds 1 pierce armor to the militia line, basically reducing the damage they get from skirmisher by 50%.

> old game

They have been releasing expansion adding new civilizations every ~6 months or so together with a bunch of balance changes.

> stay popular

It didn't. Not too such an extent as it is now. For years it had only community support and a fairly small player base. Microsoft resurrected it not so long ago.

To be fair, it may be the "biggest change ever", but it doesn't change too much. It buff some units that were bad, nerf some units and techs that were too good. But the general meta remains the same. The devs are really good at introducing changes.

It was always possible to do 18 pop feudal, but today's focus on luring deer is perhaps the biggest change to the meta?

There wasn't any real balance patch. Just people who have gotten much better at luring deer to improve early build orders. Like 3 years ago, you'd just assume 2x Boar + 8x sheep as your early food source. But today, people are adding 2x or even 3x deer to that.

As deer + boars collect food at the fastest rate, you can more consistently go up at lower villager counts. There's also much more precision: killing boars / deer / sheep under the town center more consistently today than before.

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TL;DR: Skill improved, people can do 18 pop today even though its always been possible. So people are just getting faster and more optimized.

Oh, one more thing. April patch changed Portuguese Organ Guns.

The goal of the April patch was to make organ guns more of an anti-unit shotgun, and less of a wall destroyer. So you'll see fewer organ guns on Arena (one of the few maps that start off fully stone walled).