I think gradual decay would have been better,
Agreed, it would have been better. When I was new to bitcoin I also wondered why this wasn't the case.
But I also agree it is not a good idea to change this anymore. This part should really be frozen, as changing it would worry people: if changes to coin creation are accepted, what if the community threw Satishi's idea out of the window and decided that creating an arbitrary amount of coins is a good idea?