Regarding all these parade issues, I can tell you that the problems with parades are primarily caused by WDW.
The underlying problem is that the parade designs that they use are for the most part unsuitable for the viewing environment. Any good float designer can tell you that WDW's floats are almost universally too low to the ground, given the average depth of the crowd, the fact that there are almost no high vantage points from which to watch, and very limited setback distances from the route. The floats should be designed so that the lowest of the decorated surfaces is a minimum of 3 feet off the ground -- 5 would be better. The idea being to get the bulk of the decoration and the riders above the head of the average standing adult. The fact that so much of the action takes place at ground level encourages spectators to jockey for curb position and to watch while seated on the ground; both of these behaviours are bad things from a crowd management perspective.
When crowd density is as high as it is at WDW, no spectators other than the disabled should be permitted to view the parade from a seated position. When everyone has to stand (yes, I'm including children, who either stand or are held by adults), no one will be standing in front of the seated. Strollers should be BANNED for a distance of 10-15 ft. back from the route. Having strollers in amongst the crowd is a serious evacuation hazard, especially after dark. (While I've never heard of it happening during a WDW parade, floats have been known to overheat and catch fire, especially those with enclosed engines. Float decoration components tend to give off noxious fumes if they catch fire.) What that means is that just as when you go on a ride, you take the child and the valuables out and you park the stroller in a designated storage area. It also means that the number of people who will stake out a prime spot hours in advance will be greatly reduced if they are not allowed to sit on a public thoroughfare while waiting.