Baal runs, diablo runs, mephisto grind,. cowlevel grind,.
at least diablo 3 mixed that up a bit with the power scale in terms of paragons and grinding the portals,
diablo 4 gives a few more options.
But yeah, diablo 2 has been heavy grind,
diablo 3 has been heavy grind,
diablo 4 will certainly be heavy grind as well, but with perhaps a little more variety within each tier.