Well, Disney first has to add attractions just to make up for the ones they've closed.
Turning a bit more serious, yes, upgrades to the existing theme parks are vital to addressing crowds. However, by 2025, these probably won't be enough.
A 5th Gate is not something for now. Disney has its priorities right by first addressing deficiencies at WDW's existing parks. However, given the lead times involved,
somebody better be thinking about what's needed after that.
The problem is that many corporations "manage by crisis" rather than plan ahead to avoid those crises. Yes, the upcoming plans for WDW in general and DHS specifically are great, but they should be winding down right now, not just beginning to ramp up. Disney's senior management created the problem by ignoring WDW for over a decade. It's a problem largely of their own making.
Happy 4th!