I usually don't listen to much of anything that Motortrend says, but I feel here that they actually have some valid points.
First off, as we know from insider information, it is a fact that development of the 5LS was a conflicted process. Objectively looking at the car, it's mission in the marketplace is a conflicted one compared to previous generations of LS.
Also regarding worse body integrity, I again feel they have a point here. While I haven't driven the 5LS, I can logically see this as a possibility. You've got the stiff F-Sport suspension combined with low profile run flat tires. That to me logically sounds like a recipe for a bad ride and possibly some body integrity issues. Another reason why I feel their point may be valid is that I recently had a bad experience with a used 2016 RX350 with about 50K km (about 31K miles on it). This RX (with the 20 inch rims) had a very rough ride on city roads, and I also noticed some body integrity issues cropping on. This was a regular model, it wasn't even an F-Sport, and it had regular all season Michelin tires. It had the 20 inch rims yes, but those still have a 55 profile tire on those rims. So overall I was surprised and disappointed with my experience.
Going back to the 5LS, I continue to be very against the decision to put run flats standard on the 5LS (and LC). Also run flats are standard on the UX in North America, and available in some other world markets. Outside of North America at least thankfully regular tires are available as well. Some reviews have already criticized the UX for having a harsh ride, and to be honest Motortrend is not the first outlet I've seen criticize the 5LS ride. I mean I have to keep asking...what in God's name was Lexus thinking making run flats standard on several models now? The majority of world markets do not have great roads. Countries with glass smooth roads like Japan are actually a large minority among world markets. Also in some markets like the US and Canada, roads are arguably getting worse, not better. So again, I have to ask what was Lexus thinking here? Is Akio Toyoda so desperate to ape some of the German competition who stock many of their models with standard run flats? How many existing Lexus customers worldwide were actually asking for run flat tires? I feel like this is an answer to a question most Lexus owners and buyers never asked.
Not sure what do LS and RX have in common? I dont think their rides can be compared. RX always had bad ride with big tires, LS firmer but not bad ride - plenty of members have it here. I am sure new RX will be massively improved with TNGA update.
Same goes for UX, pretty much every review says it has very composed ride, despite good and relatively flat handling.
Lexus and Toyota really managed to get the medium right, where you have good handling car that is not too stiff over the bumps...
World has changed, barges like before do not work anymore and latest Toyota and Lexus vehicles worldwide have been getting best ever review scores. New Corolla, CHR, Camry, Rav4, UX, ES have received positive reviews across different countries and continents, which never happened before.
Run flat tires seem like very old story... new ones are much better than before, and it in the, if you are buying 50k Lexus, then you can also replace the tires if you really want, but usually it makes very little difference or sense.