You are either missing the point, don't want to see it or do not have the relevant experience to see it. A unibody, independent suspension vehicle is simple inherently limited in becoming a "serious" off road vehicle. The point of sticking with a multilink, live axle, body on frame setup is to allow that to be possible, either stock or through modifications. The goal with the "Land Rover" series 5.... should be to create something that is better off road than anything on the planet and capable of being built to be able to win competitive off road races, while being acceptable to drive on road.
Creating a really nice road vehicle that costs two to three times as much as a normal vehicle that tops out at intermediate trails and is nearly impossible to modify is not the point of what a "Land Rover" was meant to be.
What is *your* point? What is a "serious" off-road vehicle, in your definition? Is it one that's "hard" to drive well? Is it one you don't *want* to drive on a long road trip to the trailhead? My D5 shames the old D1/D2/LR3/LR4 off the lot - it goes well beyond "intermediate" trails while also being a very comfortable daily driver and being easy to drive on difficult off-road trails as well. You simply refuse to acknowledge the supremacy of new technology and design born of decades of experience that Land Rover has applied - as well as the realities of maintaining road-legal certification in their largest markets, primarily from a fuel economy and emissions perspective. If they can't make it road-legal, they can't sell it, period. If I don't need to modify my truck to easily do what a modified D1/D2 can barely do, then I consider that a vast benefit - the capability is built in rather than spending tens of thousands to add it. Despite the fact that it's only entering its 3rd model year, there's already a no-cut winch available, off-road lighting, a suspension lift, underbody armor, and it easily accepts 32" M/T's without a lift...what's not to love? External accessories such as RTTs, gear carriers, etc are only a mouse click away. I've seen some shops experimenting with rock rails - but they're not done fine-tuning those yet. Another year or two and we'll see bumpers and rails that should complement the looks as well as armor it.
So tell me, do you consider the M1097A2 HMMWV a "serious off-road vehicle"? It has four-corner independent suspension for the biggest reason - to protect steering and driveline components from trail and combat damage. Is the Ford Raptor a "serious off-road vehicle"? IFS. An increasing percentage of Ultra4 racing winners, i
ncluding KOH runners are fully independent F/R - almost all have IFS. A flat underbelly gives more line choices when it provides the same ground clearance everywhere, as compared to a traditional live axle vehicle that has its highest clearance between the bell and the wheel, along the axle; and IS provides greater wheel travel. Live front axles are prone to the Death Wobble - event the newest Wrangler is experiencing it, with
Jeep issuing a statement in effect saying, "duh." IS is lighter, with lower unsprung weight. It's more stable, because articulation of one wheel doesn't impact the other wheel on that end. The only way you raise a live axle without portal axles is larger tires --- and to fit very large tires to raise the bellhousing and steering gear significantly, you need to lift the body, which raises the center of gravity and makes the vehicle less stable, unless you go the rock crawler route and widen the track so you can mount 44" boggers outside the fenders. You can still apply portals to an independently-sprung vehicle if you want to as well.
Sure, live axles have some benefits - stiffness being the primary as well as maintaining a constant ground clearance across the axle despite having less of it and less inherent travel in the suspension, but as technology marches on - metallurgy, structural engineering, etc -
independent suspension is becoming more and more advantageous.