Almost everything from the early days of higher efficiency was junk. It's not just Rheem. They went above the rest of the industry changing out burners, ignitors, ignition modules on their furnaces in the early 90s to prevent problems. No one else did that.
Why is your 40 year old shop furnace still going? Because it cost a pretty penny back then.
You can get a 90% furnace today for about the same price as some 60% furnaces 30 years ago. Adjusted for inflation, that's about the biggest steal on the market. Why are they that cheap? Cuz the manufacturers cheapened them because John Q. Public wasn't willing to pay more. Cheaper cabinetry and heat exchangers, internal components all made in 3rd world countries. I've watched HVAC sales for 13 years now. When I started selling furnaces in 1991, we weren't hammered for bottom dollar. Today it's a fight among dealers trying to undercut each other because in most cases the HO will buy the lowest bid. Look at all the people who come on here wanting to buy online to save a buck, thinking that by costing the local dealer the equipment sale will help them in the long run.
My rant is over now too :D