its not harder to cast spells in sc2. its actually much easier because u can tab through your units in a LARGE selection. i commonly put all my casters together in sc2 and tab through them to cast. also box casting heals is really difficult in wc3 because of the limits. if your healter is in control group 1 and you notice a unit in control group 2 needs healing you can’t box heal him you need to find him on the battle field because clicking an other control group cancels the cast. so u can have 1 paladin and 11 swordsman in 1 group and 12 more swordsman in 2 group. the 2nd group of 2 swordsman aren’t going to get healed as efficiently as the 1st group and there is only 1 paladin… i could go on all day with reasons the hard limit is no good and definitely not “intelligent design” as was claimed unless by intelligent you mean designed to not break video cards in the early 2000s
sc2 has 20 in the main part of the control group then little numbers to the side 1,2,3 for each group of 20 more with no hard limit and thats cause by 2012 gpus were strong enough to handle it (well supposed to be, there were lots of issues with gpus dying when it first came out) but now days even my kids laptop with 128mb video ram can play sc2 with all the optimizations they have added to it so really its no excuse for this game but at the time the optimizations hadn’t been made. it is now 2020, we deserve larger control groups and even a larger food count, and a whole army hotkey
if they were trying to entice new users they wouldn’t have brought a game from 2003 back with 0 improvements aside from graphical overhaul