I think part of the problem here is your assertion that it's "supposed to be slow"
WDW management has spent much of the last 15-20 years attempting to market and promote to flesh out the entire calender year into a consistently crowded scenario...
some of it has come from promotions...some from marketing to direct areas or segments...some from special events...some from focus on conventions or group travelling events...and some because people now fly as easily as they drive and there needs to be little reason for people to pick up and fly to florida..
Case in point this week...it should be a dead travel month, but the one federal holiday yesterday is enough to have a wave of locusts descend on WDW from the Upper Midwest and Northeast...because they have one stinking day off from school...
the walt disney world marathon is specifically designed to be in the weeks following new year...because they normally were dead.
food and wine festival in october was a brilliant move...it used to be slow...now its packed.
september is traditionally the slowest month of the year...but lo and behold...they roll out "
free dining" in 2005 and all of the sudden everyone "finds the time" to spend a week in WDW in september...
october through january are big for conventions...
may through august are big for school groups...having the cheerleading championships there is another stroke of genius
then you have golf season...six weeks of halloween and two months of christmas...six weeks of spring break...fall breaks...thanksgiving breaks
British month (september)...brazilian months (their spring summer...where its 100 there...our fall/winter...where is 75-85)
presidents day...columbus day...mardi gras...bastille day...canadian boxing day...and on and on and on
so i guess...don't let any one week of crowds influence your ideas about the need for additional gates...there really aren't that many slow times anymore.
And second, we don't have our kids in school enough
and i wholeheartedly agree with faldred....labor is THE ISSUE at wdw...there isn't enough...its never cheap enough for them...and there is no way that problem can be fixed short of huge population boom or outsourcing...
the real estate bubble really exasperated this situation...as florida is still tanked and probably was set back 10-15 years by it...because theres no way to reverese the effects of housing gambling in the sun belt...as is now painfully obvious going on 5 years later...with some aspects still getting worse.