Disney used to be very conscious of what other parks were up to. They had a big plan to contend with the opening of IOA. When it opened but did not do the attendance numbers of US, Disney stopped worrying about other parks.MGM/Hollywood Studios went up so quick they wanted to beat the opening of Universal Studios Florida.
Now they don't care anymore about the guest experience an they take their time, it's cheaper.
WDW figured it was a mature resort and had already done all the building needed. From there they focused on profits. It wasn't until HP that WDW had to deal with real competition again. They reacted slowly. They are still paying the price for that.