No, but it makes life easier. Its digital FP and allows you to get a FP for anywhere in the park. Regular FP is still available, you scan the barcode on your park ticket at the attraction and it gives you a paper with a return time now. The actual FP is in the system tied to the barcode on your park ticket.
You may not be able to prebook FPs (for me it's actually better that you can't prebook, but YMMV), but it does make it way easier to get a ton of FPs, not to mention the steps saved because you can reserve on your phone.Question on Maxpass, can you pre-book fast passes like at Disney World? Last time I was at Disneyland you couldn't, so I didn't bother to purchase it.