Blizzard tried to solve this by introducing a bunch of useless features for casuals in HoTS which ofcourse didn't work. Playing for decals is fine and all but if the core gameplay is not mad fun then you will quit the game sooner rather than later unless you are a competative person who is obsessed with improving.
Blizzard is trying in LoTV (their last chance) to introduce more micro based units and thus hoping the game will become more fun again. Sadly this will not be enough because battles will still be decided in 5 seconds due to the sick dps and low health and exceptional pathing and clumping of units.
Most of you from teamliquid will probably not agree since most are competative here but none if my irl friends would ever stick with sc2 due to this and why would they? Its so much more relaxing and fun to micro in League of Legends where if you make a mistake its not the end of the game yet that game is still highly competative. Same thing back in wc3, many of my friends like that game because it didnt stress them out completly due to the higher health and lower damage of units which leave room for lots of micro which is the highpoint of most RTS.
To save sc2 and make it GROW again Blizzard NEEDS to increase unit model collision so its not the most efficient way to clump up your entire army which will lead to more spread out armies and more skirmishes = a much better gameplay, less stress and higher skill ceiling. They need to reduce dps across the board, seeing 2 max armies battle should be an epic and interesting back and forth battle with reinforcements coming in but in its current state; Lots of explosions, one army melt and the battle lasted 5 seconds. Starcraft2 feels to me like a game of Tennis, only that its sudden death... First one to miss instantly loses the game...
Ofcourse Blizzard needs revamp the economy and mining efficiency and make it worthwhile to have 6+ bases. Without these changes this game has reached its peak already and is gonna fade away right after LoTV. Im suprised sc2 has lasted as long as it has. I just can't understand how the people at blizzard who is supposed to be the best in the industry didnt see this problem at wol beta and not even for hots. They seem totally clueless.
To Clarify: The game is not too hard for casual in its mechanics. Casuals don't need to master every mechanic to enjoy the game. The game is simply not FUN enough for casuals because casuals and new players are mostly interested in the battles and microing units and feeling awesome doing so (which is again proven by LoL). They don't care at all about complicated build orders or timings and such. I would say Broodwar is more fun for casuals than sc2 for the simple fact it has more room for micro. Casuals fighting casuals in broodwar didn't need 300 apm to enjoy a game.