Apple has increased the cellular download limit in the App Store to 200MB, up from the previous 150MB limit. The cellular limit was last increased in September 2017, from 100 MB to 150 MB.
The download limit was designed to limit the amount of data that will be downloaded from the App Store over 3G and 4G cellular data networks. The limit is designed to prevent iOS device users from downloading a huge app over their cellular connection and possibly using up their monthly data allowance or from running up data cap overage charges.
Unfortunately, users with unlimited data plans have no way to opt out of the 200MB data limit. As noted by 9to5Mac, it would be better if unlimited data users were given an option to go ahead and download an app over the 200MB limit if they so desired.
The limit leads to developers working to keep their apps under the cellular download limit, in order to reduce the chances of a user not downloading their app due to the limit.