What games should do is tell you the impact that settings have on performance. Just a text blurb that mentions how significantly you can expect a setting to matter. I’ve seen it in a few games where some settings are marked with something like heavy performance penalty but it would be nice for more things to be labeled.

Looking at something like the task manager will tell you your CPU or GPU is maxed out, but how do you know what to change to correct this? Can you just change a few barely-noticeable settings, or are you expected to replace your CPU? If the recommended is CPU X, then why is my CPU Y maxed out? If I exceed the recommended build, why is my performance so bad?

Often the recommended build is not enough to max out graphics at reasonable framerates, for example.