The age of the design, the history, and the fact that it still ranks high enough in sales to still be factory loaded by ammunition manufacturers 138 years (give or take a couple years) after it's adoption for military use should be all the information needed to answer your question.
Flexible, accurate, capable. It has taken game from small squirrels, and rabbits, to large bear, and African Plains game. Yup the 45-70's even stout enough for Africa. Since it can be loaded to equal the .458 Winchester, in a strong gun, this should not surprise anyone. During military tests in the 1870's the 45-70 loaded with a 500 grain bullet and 70 grains of black powder fired accurately over 1 mile into pine boards for penetration tests. Today it is a top competetor in 1,000 yard BPCR competitions. Hunting ranges should be kept closer to 100 or 150 yards due to the high trajectory. A really hot load runs 2,100 fps, and warm ones clock 1,400 to 1,800, and soft loads run 900 fps to 1,300 fps.
So why shouldn't everyone own a 45-70? What more could you want?