I didn't down vote you, but you've got some misconceptions.

X-mode isn't actually different gearing in the mechanical sense. It's an electronic system that optimizes the existing drivetrain components.

It doesn't provide additional gear reduction like a low-range gearbox, it adjusts the CVT's (continuously variable transmission, which doesn't even have "gears" in the traditional sense, but is a set of chains and pulleys) behavior, traction control, and power distribution, but doesn't change the fundamental gear ratios. Hill descent control is a braking function, not a gearing one.

True 4WD systems have a physically separate low range gearbox that allows the driver to physically engage different gears to vastly reduce the gear ratio to allow the vehicle to make much more efficient use of the available engine power.

You would waste far more energy trying to get an AWD Crosstrek over a boulder with X-mode than an actual 4WD vehicle with a lever to put the vehicle into 4 Wheel Low gear.

While excellent for many things, Subaru's AWD system is essentially a fancy electronic traction control system. It cannot reduce gearing to the level of a 4WD low range gear box. And that's fine! But the incorrect assumptions of people who overestimate the capabilities of their vehicles is the precise reason for the rules the NPS has in place; Subaru Crosstreks with X-Mode are gonna need to be rescued by NPS staff far more often than 4Runners with a low range gearbox.

Subaru marketing is great, but NPS roads with AWD restrictions are not rally stages in a Finland forest, they are roads with boulders or mud or deep water or sand or many other things that a 4WD vehicle will probably be able to handle, but an AWD vehicle will probably not be able to handle. And on these roads, if you get stuck, a park ranger is going to have to rescue you, at tax payer expense, because you thought your vehicle could do something that it could not.