You can have a well built lite 5er if that were the MFG's intentions. My previous 2013 Northwood Fox Mountain was a 1/2 ton type 5th wheel @1385 dry pin and 7200 lbs or so dry. Being only 27'10 long it would be easily towable by Fords new F150's that have close to 1900+ lbs of CCC.
Had it for 6 years and except for a couple very minor issues it was trouble free.
Most people are weekend warrior types anyway so a lite 5er doesn't need to stand up to the rigors of a full timer or an RV'er that hits the road for 6 months out of the year.
The same issue that lite 5ers have can also be had on non lite 5ers.
With that being said you can't lump all lite 5ers ito the same group. Some MFG's do a better job of construction that others.