We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
There are so many rating systems that it can be confusing or misleading. And when it comes to off-trail wilderness hiking, which we did a lot of in the Outer Hebrides, you really need a guide who knows the terrain to estimate what sorts of challenges you can handle. In less wilderness areas, of course, we all get a kick out of doing off-trail explorations on our own. Not always a good idea.
Many difficulty- rating systems are based on altitude changes, steepness of grade, length, agility-requirements, and risks (eg weather, cliffs, boulder fields, etc.). Other rating systems are based on technical difficulty alone.
I'll pick one example: the famous and popular Tuckerman Ravine trail up New Hampshire's Mount Washington. Alltrails rates it as Hard on their Easy/Moderate/Hard system. But what does that really mean? 9 year-olds prance up it with daypacks. What it means is that there is a substantial altitude change, variable weather (foolishly-unprepared people have died of exposure up there but it would be difficult to be that stupid), and high rocky steps at times, but it is a relatively easy hike if you are in good health and cardio condition. It's a 7-hr hike up to Lion's Head and back down - what Europeans call "hill-walking." In the European system, the Tuck hike probably would be rated in the 2 range on their 1-5 rating system.
In my view, though, those Euro ratings - "Easy" to "Expedition-Level" - do underestimate the challenges. The Euro level 2 to 2.3 range is plenty for me. On level 3, I suspect that I would be a slowpoke in a group. People do not like to have to wait for the slowpokes. On straight steep uphills, off-trail, with unstable footing, I need a minute to catch my breath every 20-30 steps. I call that "admiring the scenery" or "taking a picture."
Since we're talking about hill-walking - all-terrain hiking - and not technical mountaineering, we are mostly talking about stamina and cardio conditioning. Strength is not a major factor but mental and physical stamina are.
Photo is from the popular hill walk/climb, Breakneck Ridge Trail in the very pleasant village of Cold Spring, NY. It's a 6-mile hill walk but the first mile involves lots of scrambling and a 2000-foot altitude change which is why some people rate it at a rather high - too high - 3 because anybody in decent shape can do it.