I wonder if the 1FZ’s sluggish reputation has to do with them losing compression over the years;
I think it's simply that they're heavy and slow. Toyota always overbuilt their frames and bodies and didn't particularly pursue performance, at least with their trucks.
The Jeep Grand Cherokee ZJ had 225 hp & 300 lb-ft, with a curb weight of 3,900 Lbs. There was the seemingly rare 4.0 ZJ with 190/225, but it was 3,674 Lbs.
The Land Cruiser 1FZ-FE 80 had 212 hp & 275 ft-lb, with a curb weight of 4,760 Lbs.
The Land Rover 4.2 V8 was 200/251 at 4,574 Lbs.
5.2 ZJ 0.0576 HP/Lb
4.0 ZJ 0.0517 HP/Lb
4.5 80 0.0445 HP/Lb
4.2 LR V8 0.0437 HP/Lb
I owned a '95 ZJ. It was pretty quick for its day. It was also a POS, needed a transmission rebuild by 80k miles, ate motor mounts and coils, and plenty of maintenance was harder than the 80. For example, they put the distributor cap behind the engine, and you could barely reach it with the firewall in the way.
So yeah, the LC is a slow, heavy, overbuilt pig that you have to actively try to kill. It's a very different type of vehicle from others in its class within the North American market. By the 2000s, SUVs turned into the family muscle car class.