I am in the know your kids and yourselves and plan travel accordingly camp. Some people should probably never go to wdw- if crowds and waiting in lines make you anxious, why go? There are literally hundreds of other places to visit and in spite of what some people seem to think Disney is not something every child must or eve n should experience.
Some parents are happy to tour parks at the pace of a toddler and sit with a drink in a bench while their little one gleefully chases jumping fountains for 45 minutes. Others would feel they wasted money and vacation time if not constanlty going from ride to ride. some kids do great napping in strollers and enjoy the stimuli and change of scene at the parks, others really need their schedules and familiar envirornments.
Hard and fast rules about what age should go to theme parks or on cruises or to Europe, etc are silly (other than cruises barring infants for safety reasons in the event if a medical emergency away from land of course) Look at you and you children and evaluate4 your own needs and desires and vacation accordingly.
(FTR my kids were 10 months and almost 3 on our first family trip to WDW and on the cruise---back before
DCL even offered child care for under three year olds---we had a BLAST, I wouldn't change a thing. Worked for us)