I've been to WDW many times over many years, in every month of year except June, including most major holidays. EVERYONE who is telling you to go during a specific month is really just basing that on THEIR biases/preferences/experiences.
1. There is NO ideal season. There are advantages and disadvantages to every month.
2. Weather isn't really predictable. In short, strong storms/rain can happen year round. Though I should add, October is hurricane season, and some months tend to be wetter than others.
3. IMO, almost what matters more than actual weather, is how well acclimated you are to the weather you get. It takes your skin about 2 weeks to acclimate. If you don't/can't expose your skin to 90 degree temps, then 90 will feel hot. If you spend all your pre-trip time in climate controlled spaces, then 90 will feel hot. The same is true for cold temps. If, however, you get daily pre-trip walks in 90 degree weather, then highs of 90 can be quite enjoyable.
4. Crowds. IMO, it is a mistake to get hung up on crowd -levels. In short, WDW was built to handle crowds. Low crowd times of year have many disadvantages, IMO, like ride closures, short park hours, reduced staff, and they've had many years to work out the details. IMO, the big consideration is price; higher crowd seasons cost more... except for WDW's quiet assorted upcharges: October = MK closes early, unless you pay for the party-ticket upcharge.
5. Oddball things like bad/great CM's and illness can make/break any trip. Someone might say they had a bad trip once in July, but the reason why it was bad likely has little bearing on the outcome of YOUR trip.
Ultimately, your experience really depends on your preferences and also many random variables. Some folks hate cold, others hate heat. Great/bad staff and illnesses can happen in any season.
Ultimately, probably the only way to be certain is to try each time of year for yourself.