Sure, but why wouldn't you want your centerpiece new attraction open for the actual 50th anniversary day if it's even remotely feasible? I know I sure would, but then again, I don't run the Walt Disney Company.
And in all fairness this...
2019: Smuggler's Run & Rise of the Resistance
2020: Mickey and Minnie's Runaway Railway
2021: Remy's Ratatouille Adventure
2022: Guardians of the Galaxy: Cosmic Rewind
2023: TRON Lightcycle/Run
... is a pretty incredible and ambitious multi-year slate (setting aside the quality of the individual attractions). It's just that we know they weren't supposed to be spaced out like that, and it's only happening (if it's happening that way) to pinch pennies.