At least you didn’t have such low group limit in C&C.
It’s OK most of the time in StarCraft (which limits you to 12 units per group) but playing Zerg sometimes gets quite annoying.
Anything that allows you to select multiple units by dragging evidently has modern mouse controls with regard to group selection, even if group size may be limited. 
But I was specifically responding to the implicit suggestion that you need right click to be modern, when it’s just the traditional C&C style vs WC2-style divide. (Admittedly it did take me a few minutes to get back into C&C style, but that’s just because StarCraft usurped basically all RTS.)