No, you are mistaken. The whole world has gone to IRS.
Sequioa = (on par) Range Rover/Patrol/Expedition/G-Glass/Q Audis
Land Cruiser = (on par) low class Chevy Tahoe
The world has gone to IRS because it offers a smoother ride.
The Land Cruiser is not intended to be a pander-to-people car. While it certainly has features that make it so, it's primary purpose is to beat a trail through the Amazon jungle and laugh while it does it.
The reason Toyota put IFS on the LC starting in 1998 is because smooth rides were a major selling point. People didn't care about huge-and-indestructible as much.
Toyota knew IFS vehicles couldn't take as much abuse as their solid-axle counterparts, so they tried to compromise on the 100-series. IFS, but the control arms are MASSIVE. It'll take more force to break one on an LC than it will on a Sequoia. Same holds true for the 200. Put a Sequoia and a Land Cruiser side-by-side and look underneath. The control arms on the LC will be bigger and tougher.
Why do you think the Middle-East spec 105-series cruisers are solid front axle? Because people out there know what tough is. They don't care about ride quality in a vehicle that is designed for pure toughness.
The same reason is probably why Nissan never sold the Patrol in the US. "Oh, the ride quality suck," say the Americans.
And wait... Why do Jeep Wranglers continue to sell more than Land Cruisers or FJCruisers? Because the off-road junkies know that solid axles are stronger and more dependable than independent suspension.
Whoops, you lose again. Land Cruiser > Sequoia.
This is fun.