Here is a novel idea. Do your homework. There is a lot of information out there. The SPS has write-ups of all their trips with a lot of extra discussions. Any rating system will be subjective, change under different conditions, and the physical difficulty can often be mitigated by simply slowing down. Another novel idea - if you get to a pass that is over your head, simply turn around and find a detour.
As some know, I have written an off-trail guidebook for the Wind Rivers. I present route segments, each with a rating. Trails are broken into A,B and C. A is a currently maintained trail. B is a non-maintained trail. Both A and B trails are shown on USGS and/or Forest Service maps. C is a use-trail or well defined game trail where you have to do your own navigation to find the trails which often disappear and reappear. Off trail is broken into G, PG and R. I give descriptions and photographs of typical types of terrain. G is the most common off-trail - relatively easy to navigate, user-friendly talus, not hideously steep, and overall safe and can be done even in foul weather. PG has one or more difficulties - large talus blocks, difficult navigation, bushwhacking, very steep. It is generally terrain that beginning off-trail backpackers have a great deal of difficulty with. On PG terrain, a fall or slip it is more probable that you will break a leg or have a serious injury. On R terrain, talus blocks become large enough that you actually have to scramble or do class 3 moves, steepness becomes exposed to the point where you could die if you fall. The R designation is primarily a safety issue and includes permanent snowfields, glaciers, unstable moraines. R rated terrain is not safe to do in a storm. There are only a handful of R-rated passes that I use and I give LOTS of heads-up, steering those not capable to easier routes. One thing nice about writing a guidebook is that I can be the dictator and use any rating system I want!