Hormones are way too complicated to take a blanket approach like this. For total testosterone 250ng/dl is low, 400ng/dl might be low, but it depends on a lot of other factors - including symptoms. A man with 600ng/dl might be "normal" but not "healthy." In 2022, it seems normal to be not healthy in many cases, but it may not necessarily be desirable to be "normal."
I'm not well-educated on hormone replacement, but I know enough to know there aren't easy answers except "if you are symptomatic as a result of hormone deficiencies, you can (and probably should) get it treated"