Its pretty good if you plan it.
Trondheim and Oslo already do this.
There is caveats:
1. There must exist some parking and public transportation option that connects it somewhere. I.e entire downtown for parking, or a bus route that isn't cancerous, or a tram, or a subway
2. If its too big, there is only trade/shop facilities on the outskirt, meaning its a office only area
3. There is going to be a parking house bordering it. Or nobody in management of corporations is even going to look towards it
4. You must be able to walk or bike from neighbor districts to this area, without it being special or tedious. If the city infrastructure is fucked in the first place, a walk only zone won't save it